publicationDate stringlengths 10 10 | title stringlengths 17 233 | abstract stringlengths 20 3.22k | id stringlengths 9 12 |
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2006-11-28 | Energy Transport between Hole Gas and Crystal Lattice in Diluted Magnetic Semiconductor | The temperature dependent energy transfer rate between charge carriers and
lattice has been experimentally investigated in ferromagnetic semiconductors.
Studied 100 nm thick low-temperature MBE grown Mn_{x}Ga_{1-x}As samples had
manganese concentrations x=3.7 % and 4.0 %. Curie temperatures estimated from
temperatures of peak resistivities were 60 K and 62 K, respectively. | 0611704v1 |
2006-12-01 | Vortex motion in chilarity-controlled pair of magnetic disks | We investigate the influence of the vortex chirality on the magnetization
processes of a magnetostatically coupled pair of magnetic disks. The magnetic
vortices with opposite chiralities are realized by introducing asymmetry into
the disks. The motion of the paired vortices are studied by measuring the
magnetoresistance with lock-in resistance bridge technique. The vortex
annihilation process is found to depend on the moving directions of the
magnetic vorticies. The experimental results are well reproduced by the
micromagnetic simulation. | 0612023v1 |
2006-12-01 | Microscopic and Macroscopic Signatures of Antiferromagnetic Domain Walls | Magnetotransport measurements on small single crystals of Cr, the elemental
antiferromagnet, reveal the hysteretic thermodynamics of the domain structure.
The temperature dependence of the transport coefficients is directly correlated
with the real-space evolution of the domain configuration as recorded by x-ray
microprobe imaging, revealing the effect of antiferromagnetic domain walls on
electron transport. A single antiferromagnetic domain wall interface resistance
is deduced to be of order $5\times10^{-5}\mathrm{\mu\Omega\cdot cm^{2}}$ at a
temperature of 100 K. | 0612039v1 |
2006-12-06 | Plasma-Like Negative Capacitance in Nano-Colloids | A negative capacitance has been observed in a nano-colloid between 0.1 and
10^-5 Hz. The response is linear over a broad range of conditions. The
low-omega dispersions of both the resistance and capacitance are consistent
with the free-carrier plasma model, while the transient behavior demonstrates
an unusual energy storage mechanism. A collective excitation, therefore, is
suggested. | 0612160v1 |
2006-12-11 | Theoretical study of doped-Tl$_{2}$Mn$_{2}$O$_{7}$ and Tl$_{2}$Mn$_{2}$O$_{7}$ under pressure | Using first-principles density functional based calculations, we study the
effect of doping and pressure in manganese based pyrochlore
compound,Tl$_{2}$Mn$_{2}$O$_{7}$ that exhibits colossal magneto-resistive
behavior. The theoretical study is motivated by the counter-intuitive
experimental observation of suppression of ferromagnetic transition temperature
upon application of pressure and its enhancement upon substitution of Mn by
moderate amount of nonmagnetic Sb ion. We also attempt to resolve the issue
related to crystal structure changes that may occur upon application of
pressure. | 0612245v2 |
2006-12-31 | Thermal rectifying effect in two dimensional anharmonic lattices | We study thermal rectifying effect in two dimensional (2D) systems consisting
of the Frenkel Kontorva (FK) lattice and the Fermi-Pasta-Ulam (FPU) lattice. It
is found that the rectifying effect is related to the asymmetrical interface
thermal resistance. The rectifying efficiency is typically about two orders of
magnitude which is large enough to be observed in experiment. The dependence of
rectifying efficiency on the temperature and temperature gradient is studied.
The underlying mechanism is found to be the match and mismatch of the spectra
of lattice vibration in two parts. | 0701015v1 |
2007-01-18 | On the origin of unusual transport properties observed in densely packed polycrystalline CaAl_{2} | A possible origin of unusual temperature behavior of transport coefficients
observed in densely packed polycrystalline CaAl_{2} compound [M. Ausloos et
al., J. Appl. Phys. 96, 7338 (2004)] is discussed, including a power-like
dependence of resistivity with $\rho \propto T^{-3/4}$ and N-like form of the
thermopower. All these features are found to be in good agreement with the
Shklovskii-Efros localization scenario assuming polaron-mediated hopping
processes controlled by the Debye energy. | 0701456v1 |
2007-01-24 | Graphene Nano-Ribbon Electronics | We have fabricated graphene nano-ribbon field-effect transistor devices and
investigated their electrical properties as a function of ribbon width. Our
experiments show that the resistivity of a ribbon increases as its width
decreases, indicating the impact of edge states. Analysis of temperature
dependent measurements suggests a finite quantum confinement gap opening in
narrow ribbons. The electrical current noise of the graphene ribbon devices at
low frequency is found to be dominated by the 1/f noise. | 0701599v1 |
2007-03-07 | Current sharing between superconducting film and normal metal | A two-dimensional model is introduced that describes current sharing between
the superconducting and normal metal layers in configuration typical of
YBCO-coated conductors. The model is used to compare the effectiveness of
surround stabilizer and more conventional one-sided stabilizer. When the
resistance of the interface between the superconductor and stabilizer is low
enough, the surround stabilizer is less effective than the one-sided stabilizer
in stabilizing a hairline crack in the superconducting film. | 0703193v1 |
2007-03-12 | Effect of Polarized Current on the Magnetic State of Antiferromagnet | We provide evidence for the effects of spin polarized current on a
nanofabricated antiferromagnet incorporated into a spin-valve structure.
Signatures of current-induced effects include bipolar steps in differential
resistance, current-induced changes of exchange bias correlated with these
steps, and deviations from the statistics expected for thermally activated
switching of spin valves. We explain our observations by a combination of spin
torque exerted on the interfacial antiferromagnetic moments, and
electron-magnon scattering in antiferromagnet. | 0703281v2 |
2007-04-14 | Biased Structural Fluctuations due to Electron Wind Force | Direct correlation between temporal structural fluctuations and electron wind
force is demonstrated, for the first time, by STM imaging and analysis of
atomically-resolved motion on a thin film surface under large applied current
(10e5 Amp/sqare cm). The magnitude of the momentum transfer between current
carriers and atoms in the fluctuating structure is at least five to fifteen
times (plus or minus one sigma range) larger than for freely diffusing adatoms.
The corresponding changes in surface resistivity will contribute significant
fluctuation signature to nanoscale electronic properties. | 0704.1852v1 |
2007-04-25 | Pressure induced magnetic ordering in Yb2Pd2Sn with two quantum critical points | Pressure induced long range antiferromagnetic order is discovered in Yb2Pd2Sn
by measuring the electrical resistivity under pressure up to 5.0 GPa. Magnetic
ordering is observed above about 1.0 GPa, being the lowest pressure in
Yb-intermetallics showing pressure induced magnetic ordering, Unexpectedly,
ordering disappears above about 4.0 GPa, giving rise to the first observation
of the appearance of two quantum critical points persisting in a broad range of
pressure within a single material. | 0704.3307v2 |
2007-06-10 | Scattering of charge carriers by point defects in bilayer graphene | Theory of scattering of massive chiral fermions in bilayer graphene by radial
symmetric potential is developed. It is shown that in the case when the
electron wavelength is much larger than the radius of the potential the
scattering cross-section is proportional to the electron wavelength. This leads
to the mobility independent on the electron concentration. In contrast with the
case of single-layer, neutral and charged defects are, in general, equally
relevant for the resistivity of the bilayer graphene. | 0706.1351v2 |
2007-06-19 | Resistive state of quasi-one-dimensional superconductors: fluctuations vs. sample inhomogeneity | The shape of experimentally observed R(T) transition of thin superconducting
wires is analyzed. Broadening of the transition in quasi-1-dimensional
superconducting channels is typically associated with phase slip mechanism
provided by thermal or quantum fluctuations. It is shown that consideration of
inevitable geometrical inhomogeneity and finite dimensions of real samples
studied in experiments is of primary importance for interpretation of results.
The analysis is based on experimental fact that for many superconducting
materials the critical temperature is a function of characteristic dimension of
a low-dimensional system: film thickness or wire cross section | 0706.2779v1 |
2007-08-03 | Nonlocal Charge Transport Mediated by Spin Diffusion in the Spin-Hall Effect Regime | A nonlocal electric response in the spin-Hall regime, resulting from spin
diffusion mediating charge conduction, is predicted. The spin-mediated
transport stands out due to its long-range character, and can give dominant
contribution to nonlocal resistance. The characteristic range of nonlocality,
set by the spin diffusion length, can be large enough to allow detection of
this effect in materials such as GaAs despite its small magnitude. The
detection is facilitated by a characteristic nonmonotonic dependence of
transresistance on the external magnetic field, exhibiting sign changes and
decay. | 0708.0455v1 |
2007-09-11 | Co/Nb/Co low field superconducting spin switch | We report experiments on a superconducting spin switch based on
technologically relevant materials as elemental ferromagnetic Co and elemental
superconducting Nb. The Co/Nb/Co structure exhibits inverse spin switch effect,
can be operated at liquid helium temperature and can switch from
superconductive to normal state in rather weak applied magnetic fields.
Relevant critical currents as a function of temperature and magnetic field as
well as preparation of superconductive or resistive state are addressed here. | 0709.1687v1 |
2007-09-12 | Dynamic Thermal Analysis of a Power Amplifier | This paper presents dynamic thermal analyses of a power amplifier. All the
investigations are based on the transient junction temperature measurements
performed during the circuit cooling process. The presented results include the
cooling curves, the structure functions, the thermal time constant distribution
and the Nyquist plot of the thermal impedance. The experiments carried out
demonstrated the influence of the contact resistance and the position of the
entire cooling assembly on the obtained results. | 0709.1818v1 |
2007-09-20 | A Kondo lattice antiferromagnet CePd5Al2 | We report on the electrical resistivity, magnetic susceptibility and
heat-capacity measurements on a new intermetallic compound CePd5Al2,
crystallizing in the ZrNi2Al5-type tetragonal structure, with lattice
parameters a = 4.156 A and c = 14.883 A. The compound presents Kondo lattice
behavior and an easy-plane antiferromagnetic ground state with two magnetic
transitions at 2.9 K and 3.9 K. The Sommerfeld coefficient is estimated as 60
mJ/mol K^2. | 0709.3135v1 |
2007-09-24 | Magnetoresistance in an all-manganite heterostructure | We study the magnetic and transport properties of all-manganite
heterostructures consisting of ferromagnetic metallic electrodes separated by
an antiferromagnetic barrier. We find that the magnetic ordering in the barrier
is influenced by the relative orientation of the electrodes magnetization
producing a large difference in resistance between the parallel and
antiparallel orientations of the ferromagnetic layers. The external application
of a magnetic field in a parallel configuration also leads to large
magnetoresistance. | 0709.3720v1 |
2007-11-06 | Barrier breakdown in a multiple quantum well structure | We explore a regime of unipolar electronic transport in a multiple quantum
well structure with very large current discontinuities - up to five orders of
magnitude. Magneto-transport experiments reveal different transport regimes.
Quantum well impact ionization shifts the structure from a resistive down
state, where the current flows through inter-well quantum tunneling, to a
highly conductive up state. In the latter regime, the current leaks through a
barrier suddenly broken down because of an efficient ionization of the first
quantum well. | 0711.0890v1 |
2007-11-08 | Substrate limited electron dynamics in graphene | We study the effects of polarizable substrates such as SiO2 and SiC on the
carrier dynamics in graphene. We find that the quasiparticle spectrum acquires
a finite broadening due to the long-range interaction with the polar modes at
the interface between graphene and the substrate. This mechanism results in a
density dependent electrical resistivity, that exhibits a sharp increase around
room temperature, where it can become the dominant limiting factor of electron
transport. The effects are weaker in doped bilayer graphene, due to the more
conventional parabolic band dispersion. | 0711.1303v3 |
2007-11-28 | Evidence for Two Current Conduction in Iron | Measurements of resistivities of dilute iron based alloys show strong
deviations from Matthiessen's rule. These deviations can be explained by a
model in which spin up and spin down electrons conduct in parallel. The results
are consistent with the theory of impurity shielding in these alloys. [This
1967 paper provides the first experimental demonstration of two current
conduction at low temperatures in a ferromagnetic metal. One direct consequence
of this property is the Giant Magnetoresistance discovered in 1988 by the
groups of Albert Fert and of Peter Gr\"unberg]. | 0711.4478v1 |
2007-12-12 | Magnetic phase transition and magnetocaloric effect in PrCo9Si4 and NdCo9Si4 | The compounds, PrCo9Si4 and NdCo9Si4, have been recently reported to exhibit
first-order ferromagnetic transitions near 24 K. We have subjected this
compound for further characterization by magnetization, heat-capacity and
electrical resistivity measurements at low temperatures in the presence of
magnetic fields, particularly to probe magnetocaloric effect and
magnetoresistance. The compounds are found to exhibit rather modest
magnetocaloric effect at low temperatures peaking at Curie temperature,
tracking the behavior of magnetoresistance. The magnetic transition does not
appear to be first order in its character. | 0712.1989v1 |
2008-01-09 | Colossal Positive Magnetoresistance in a Doped Nearly Magnetic Semiconductor | We report on a positive colossal magnetoresistance (MR) induced by
metallization of FeSb$_{2}$, a nearly magnetic or "Kondo" semiconductor with 3d
ions. We discuss contribution of orbital MR and quantum interference to
enhanced magnetic field response of electrical resistivity. | 0801.1354v1 |
2008-03-27 | Current-induced persistent magnetization in a relaxorlike manganite | A single crystal of 7% Fe-doped
(La$_{0.7}$Pr$_{0.3}$)$_{0.65}$Ca$_{0.35}$MnO$_3$ shows up as a typical relaxor
ferromagnet, where ferromagnetic metallic and charge-orbital-ordered insulating
clusters coexist with controllable volume fraction by external stimuli. There,
the persistent ferromagnetic metallic state can be produced by an
electric-current excitation as the filamentary region, the magnetization in
which is increased by ~0.4$\mu_{\rm B}$ per Mn. A clear distinction from the
current heating effect in a magnetic field, which conversely leads to a
decrease in ferromagnetic fraction, enables us to bi-directionally switch both
the magnetization and resistance by applying the voltages with different
magnitudes. | 0803.3922v1 |
2008-03-30 | Organized Current Patterns in Disordered Conductors | We present a general theory of current deviations in straight current
carrying wires with random imperfections, which quantitatively explains the
recent observations of organized patterns of magnetic field corrugations above
micron-scale evaporated wires. These patterns originate from the most efficient
electron scattering by Fourier components of the wire imperfections with
wavefronts along the $\pm 45^{\circ}$ direction. We show that long range
effects of surface or bulk corrugations are suppressed for narrow wires or
wires having an electrically anisotropic resistivity. | 0803.4307v1 |
2008-05-16 | Frictional Duality Observed during Nanoparticle Sliding | One of the most fundamental questions in tribology concerns the area
dependence of friction at the nanoscale. Here, experiments are presented where
the frictional resistance of nanoparticles is measured by pushing them with the
tip of an atomic force microscope. We find two coexisting frictional states:
While some particles show finite friction increasing linearly with the
interface areas of up to 310,000nm^2, other particles assume a state of
frictionless sliding. The results further suggest a link between the degree of
surface contamination and the occurrence of this duality. | 0805.2448v2 |
2008-05-28 | Extraordinary sensitivity of the electronic structure and properties of single-walled carbon nanotubes to molecular charge-transfer | Interaction of single-walled carbon nanotubes with electron donor and
acceptor molecules causes significant changes in the electronic and Raman
spectra, the relative proportion of the metallic species increasing on electron
donation through molecular charge transfer, as also verified by electrical
resistivity measurements. | 0805.4239v1 |
2008-06-10 | Thermal contact resistance between two nanoparticles | We compute the thermal conductance between two nanoparticles in contact based
on the Molecular Dynamics technique. The contact is generated by letting both
particles stick together under van der Waals attractions. The thermal
conductance is derived from the fluctuation-dissipation theorem and the time
fluctuations of the exchanged power. We show that the conductance is
proportional to the atoms involved in the thermal interaction. In the case of
silica, the atomic contribution to the thermal conductance is in the range of
0.5 to 3 nW.K-1. This result fits to theoretical predictions based on
characteristic times of the temperature fluctuation. The order of magnitude of
the contact conductance is 1 \mu W.K-1 when the cross section ranges from 1 to
10nm2. | 0806.1609v1 |
2008-06-25 | Morphology and flexibility of graphene and few-layer graphene on various substrates | We report on detailed microscopy studies of graphene and few-layer-graphene
produced by mechanical exfoliation on various semi-conducting substrates. We
demonstrate the possibility to prepare and analyze graphene on (001)-GaAs,
manganese p-doped (001)-GaAs and InGaAs substrates. The morphology of graphene
on these substrates was investigated by scanning electron and atomic force
microscopy and compared to layers on silicon oxide. It was found that graphene
sheets strongly follow the texture of the sustaining substrates independent on
doping, polarity or roughness. Furthermore resist residues exist on top of
graphene after a lithographic step. The obtained results provide the
opportunity to research the graphene-substrate interactions. | 0806.4074v1 |
2008-06-25 | Hidden Orbital Liquid State Within Ferromagnetically Ordered Metallic SrRuO3 | We have experimentally found related anomalies in electrical resistivity, dc
and ac magnetic susceptibility, appearing deeply within ferromagnetically
ordered state in SrRuO3. Lack of Jahn-Teller distortion in this regime rules
out conventional orbital order, forcing one to describe these in terms of an
orbital liquid ground state coexisting with ferromagnetic spin order. We
suggest that weak spin-orbit coupling in such an unusual state underpins the
observed anomalies. | 0806.4198v1 |
2008-07-29 | Control of heat transport in quantum spin systems | We study heat transport in quantum spin systems analytically and numerically.
First, we demonstrate that heat current through a two-level quantum spin system
can be modulated from zero to a finite value by tuning a magnetic field.
Second, we show that a spin system, consisting of two dissimilar parts - one is
gapped and the other is gapless, exhibits current rectification and negative
differential thermal resistance. Possible experimental realizations by using
molecular junctions or magnetic materials are discussed. | 0807.4575v1 |
2008-07-31 | Superconductivity in nickel-based compound GdONiBi and hole doped Gd0.9Sr0.1ONiBi | We successfully synthesized the nickel-based compound GdONiBi with
superconducting transition temperature about 4.5 K. By partially substituting
the element Gd with Sr to introduce holes into the material, we got new
superconductor Gd0.9Sr0.1ONiBi with critical temperature about 4.7 K. The
normal state resistivity in nickel-based samples shows a metallic behavior. The
magnetoresistance measurements show a different behavior compared to those in
iron-based compounds which indicates that the mechanism in the two kinds of
superconductors maybe different. | 0807.5045v1 |
2008-09-11 | Koshino-Taylor effect in graphene | We discuss the phonon-assisted scattering of electrons by defects, i.e., the
so-called Koshino-Taylor effect, in graphene. The two-dimensional character of
graphene implies that the strength of the Koshino-Taylor effect can be
considerably larger than in ordinary metals. We show that at finite
temperatures the defect-induced resistivity formally diverges in the
thermodynamic limit, having a non-analytic $T\ln T$ component when finite size
effects are taken into account. | 0809.1996v2 |
2008-10-10 | Hysteresis in the electronic transport of V2O3 thin films: non-exponential kinetics and range scale of phase coexistence | The thermal hysteresis of the electronic transport properties were studied
for V2O3 thin films. The temporal evolution of the resistance shows the
out-of-equilibrium nature of this hysteresis with a very slow relaxation.
Partial cycles reveal not only a behavior consistent with phase coexistence,
but also the presence of spinodal temperatures which are largely separated. The
temperature spreading of phase coexistence is consistent with the bulk phase
diagram in the pressure-temperature plane, confirming that the film is
effectively under an effective pressure induced by the substrate. | 0810.1868v1 |
2008-11-19 | Nonlocal Spin Transport in Lateral Spin Valves with Multiple Ferromagnetic Electrodes | We study the nonlocal spin transport in a lateral spin valve with multiple
ferromagnetic (FM) electrodes. When two current-injecting and two spin
current-detecting electrodes are all ferromagnetic, the number of possible
nonlocal spin signal states is four at maximum. In reality, this number is
reduced, depending on the inter-probe distance and the relative magnitudes of
the spin resistances. Our theoretical results are in agreement with recent
experiments of spin injection into an Al island, a carbon nanotube, and
graphene. | 0811.3138v1 |
2009-02-24 | Analysis of the Conduction Heat Transfer in Cantilevers under Steady State Cryogenic Conditions | An accurate analysis of the conduction heat transfer in a cryogenic flask is
made and some useful formulae are derived. Taking into account the temperature
dependence of conductivity and tensile strength of the supporting rods for a
helium cryostat, these formulae may provide more exact results than the the
formulae based on simpler models. This allows the design of the supporting
elements of a liquid helium cryostat with minimum cross-section (for minimizing
the heat transfer)and proper mechanical resistance. Some examples of numerical
results and tables are also presented. | 0902.4144v1 |
2009-03-23 | Spin-polarized electronic structures and transport properties of Fe-Co alloys | The electrical resistivities of Fe-Co alloys owing to random alloy disorder
are calculated using the Kubo-Greenwood formula. The obtained electrical
esistivities agree well with experimental data quantitatively at low
temperature. The spin-polarization of Fe50Co50 estimated from the conductivity
(86%) has opposite sign to that from the densities of the states at the Fermi
level (-73%). It is found that the conductivity is governed mainly by
s-electrons, and the s-electrons in the minority spin states are less
conductive due to strong scattering by the large densities of the states of
d-electrons than the majority spin electrons. | 0903.3842v1 |
2009-04-15 | Nonvolatile memory effects in hybrid devices of few-layer graphene and ferroelectric polymer films | We report on the fabrication and electrical characterization of few-layer
graphene (FLG) devices coated with a ferroelectric polymer layer of
poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)]. Highly stable and
reliable resistance changes were observed under floating conditions, which were
dependent on the back gate voltage applied beforehand. Nonvolatile memory
functionality in the hybrid FLG-P(VDF/TrFE) devices is attributed to a remanent
electric field induced by the ferroelectric polarization of the P(VDF/TrFE)
layer. | 0904.2242v1 |
2009-04-15 | Quasiparticle Transformation During a Metal-Insulator Transition in Graphene | Here we show, with simultaneous transport and photoemission measurements,
that the graphene terminated SiC(0001) surface undergoes a metal-insulator
transition (MIT) upon dosingwith small amounts of atomic hydrogen. We find the
room temperature resistance increases by about 4 orders of magnitude, a
transition accompanied by anomalies in the momentum-resolved spectral function
including a non-Fermi Liquid behaviour and a breakdown of the quasiparticle
picture. These effects are discussed in terms of a possible transition to a
strongly (Anderson) localized ground state. | 0904.2249v1 |
2009-05-14 | Galvanomagnetic properties and noise in a barely metallic film of V2O3 | We have measured the magnetotransport properties of a strained metallic V2O3
thin film. Most of the properties are similar to V2O3 single crystals that have
been submitted to a large pressure. In addition, resistance noise analysis
indicates that conductivity fluctuations are freezing out at T\approx 10K.
Examination of a range of measurements leads to the conclusion that
spins-configuration fluctuations dominate in the low temperature regime. | 0905.2290v1 |
2009-05-25 | Photocurrent Properties of Freely Suspended Carbon Nanotubes under Uniaxial Strain | The photocurrent properties of freely suspended single-walled carbon
nanotubes (CNTs) are investigated as a function of uniaxial strain. We observe
that at low strain, the photocurrent signal of the CNTs increases for
increasing strain, while for large strain, the signal decreases, respectively.
We interpret the non-monotonous behavior by a superposition of the influence of
the uniaxial strain on the resistivity of the CNTs and the effects caused by
Schottky contacts between the CNTs and the metal contacts. | 0905.3952v1 |
2009-06-23 | Breakdown Current Density of Graphene Nano Ribbons | Graphene nanoribbons (GNRs) with widths down to 16 nm have been characterized
for their current-carrying capacity. It is found that GNRs exhibit an
impressive breakdown current density, on the order of 10^8 A/cm2. The breakdown
current density is found to have a reciprocal relationship to GNR resistivity
and the data fit points to Joule heating as the likely mechanism of breakdown.
The superior current-carrying capacity of GNRs will be valuable for their
application in on-chip electrical interconnects. The thermal conductivity of
sub-20 nm graphene ribbons is found to be more than 1000 W/m-K. | 0906.4156v1 |
2009-07-07 | Quantum oscillations in a topological insulator Bi_{1-x}Sb_{x} | We have studied transport and magnetic properties of Bi_{1-x}Sb_x, which is
believed to be a topological insulator - a new state of matter where an
insulating bulk supports an intrinsically metallic surface. In nominally
insulating Bi_{0.91}Sb_{0.09} crystals, we observed strong quantum oscillations
of the magnetization and the resistivity originating from a Fermi surface which
has a clear two-dimensional character. In addition, a three-dimensional Fermi
surface is found to coexist, which is possibly due to an unusual coupling of
the bulk to the surface. This finding demonstrates that quantum oscillations
can be a powerful tool to directly probe the novel electronic states in
topological insulators. | 0907.1125v1 |
2009-07-17 | Calculation of Cu/Ta interface electron transmission and effect on conductivity in nanoscale interconnect technology | Resistivity augmentation in nanoscale metal interconnects is a performance
limiting factor in integrated circuits. Here we present calculations of
electron scattering and transmission at the interface between Cu interconnects
and their barrier layers, in this case Ta. We also present a semiclassical
model to predict the technological impact of this scattering and find that a
barrier layer can significantly decrease conductivity, consistent with
previously published measurements. | 0907.2999v2 |
2009-07-22 | Magnetoresistive junctions based on epitaxial graphene and hexagonal boron nitride | We propose monolayer epitaxial graphene and hexagonal boron nitride (h-BN) as
ultimate thickness covalent spacers for magnetoresistive junctions. Using a
first-principles approach, we investigate the structural, magnetic and spin
transport properties of such junctions based on structurally well defined
interfaces with (111) fcc or (0001) hcp ferromagnetic transition metals. We
find low resistance area products, strong exchange couplings across the
interface, and magnetoresistance ratios exceeding 100% for certain chemical
compositions. These properties can be fine tuned, making the proposed junctions
attractive for nanoscale spintronics applications. | 0907.3952v1 |
2009-08-20 | Scattering of charge carriers in graphene induced by topological defects | We study the scattering of graphene quasiparticles by topological defects,
represented by holes, pentagons and heptagons. For holes, we found that at low
concentration they give a negligible contribution to the resistivity. Whenever
pentagons or heptagons are introduced we realize that a fermionic current is
scattered by defects. | 0908.2979v2 |
2009-08-31 | Tuning the graphene work function by electric field effect | We report variation of the work function for single and bi-layer graphene
devices measured by scanning Kelvin probe microscopy (SKPM). Using the electric
field effect, the work function of graphene can be adjusted as the gate voltage
tunes the Fermi level across the charge neutrality point. Upon biasing the
device, the surface potential map obtained by SKPM provides a reliable way to
measure the contact resistance of individual electrodes contacting graphene. | 0909.0020v2 |
2009-09-25 | A large magnetoinductance effect in La0.67Ba0.33MnO3 | We report four probe impedance of La0.67Ba0.33MnO3 at f = 100 kHz under
different dc bias magnetic fields. The ac resistance (R) exhibits a peak around
Tp = 325 K which is accompanied by a rapid increase and a peak in the reactance
(X) in a zero field. The magnetoreactance exhibits a sharp peak close to Tp and
its magnitude (= 60% in H = 1 kG) exceeds that of the ac magnetoresistance (= 5
% inH = 1 kG). It is suggested that the magnetoreactance arises from changes in
the self inductance of the sample rather than the capacitance. | 0909.4614v1 |
2009-10-04 | Theory of thermally activated vortex bundles flow over the directional-dependent potential barriers in type-II superocnductors | The thermally activated vortex bundle flow over the directional-dependent
energy barrier in type-II superconductors is investigated. The coherent
oscillation frequency and the mean direction of the random collective pinning
force of the vortex bundles are evaluated by applying the random walk theorem.
The thermally activated vortex bundle flow velocity is obtained.The
temperature- and field-dependent Hall and longitudinal resistivities induced by
the bundle flow for type-II superconducting bulk materials and thin films are
calculated. All the results are in agreement with the experiments. | 0910.0581v3 |
2009-10-13 | Voltage Asymmetry of Spin-Transfer Torques | We present a Non-Equilibrium Green's Function based model for spin torque
transfer (STT) devices which provides quantitative agreement with
experimentally measured (1) differential resistances, (2) Magnetoresistance
(MR), (3) In-plane torque and (4) out-of-plane torque over a range of bias
voltages, using a single set of three adjustable parameters. We believe this is
the first theoretical model that is able to cover this diverse range of
experiments and a key aspect of our model is the inclusion of multiple
transverse modes. We also provide a simple explanation for the asymmetric bias
dependence of the in-plane torque, based on the polarization of the two
contacts in energy range of transport. | 0910.2489v1 |
2009-10-21 | Low-temperature ballistic transport in nanoscale epitaxial graphene cross junctions | We report on the observation of inertial-ballistic transport in nanoscale
cross junctions fabricated from epitaxial graphene grown on SiC(0001).
Ballistic transport is indicated by a negative bend resistance of R12,43 ~ 170
ohm which is measured in a non-local, four-terminal configuration at 4.2 K and
which vanishes as the temperature is increased above 80 K. | 0910.4010v1 |
2009-10-24 | Inducing Chalcogenide Phase Change with Ultra-Narrow Carbon Nanotube Heaters | Carbon nanotube (CNT) heaters with sub-5 nm diameter induce highly localized
phase change in Ge2Sb2Te5 (GST) chalcogenide. A significant reduction in
resistance of test structures is measured as the GST near the CNT heater
crystallizes. Effective GST heating occurs at currents as low as 25 uA,
significantly lower than in conventional phase change memory with metal
electrodes (0.1-0.5 mA). Atomic force microscopy reveals nucleation sites
associated with phase change in GST around the CNT heater. Finite element
simulations confirm electrical characteristics consistent with the experiments,
and reveal the current and phase distribution in GST. | 0910.4672v2 |
2009-11-09 | Anomalous Nernst effect and heat transport by vortex vacancies in granular superconductors | We study the Nernst effect due to vortex motion in two-dimensional granular
superconductors using simulations with Langevin or resistively shunted
Josephson-junction dynamics. In particular, we show that the geometric
frustration of both regular and irregular granular materials can lead to
thermally driven transport of vortices from colder to hotter regions, resulting
in a sign reversal of the Nernst signal. We discuss the underlying mechanisms
of this anomalous behavior in terms of heat transport by mobile vacancies in an
otherwise pinned vortex lattice. | 0911.1628v2 |
2010-01-19 | Competing contributions of superconducting and insulating states in Ag5Pb2O6/CuO composite | The composite material, consisting of metallic particles Ag5Pb2O6 diluted in
insulating CuO matrix, has been investigated in a narrow concentration range
separating ballistic tunnel transport from hopping conductivity. The formation
of intergrain conducting bridges between metallic particles has been avoided by
a careful metallurgic treatment. Resistivity is indicated by temperature
dependence lnR~(T0/T)^1/2, and this dependence appeals an attention for
possible one dimensional conductivity which could be looked upon as a property
uniquely associated with an onset of the superconductivity extending up to Tc ~
356 K. | 1001.3185v1 |
2010-01-28 | Electrical observation of a tunable band gap in bilayer graphene nanoribbons at room temperature | We investigate the transport properties of double-gated bilayer graphene
nanoribbons at room temperature. The devices were fabricated using conventional
CMOS-compatible processes. By analyzing the dependence of the resistance at the
charge neutrality point as a function of the electric field applied
perpendicular to the graphene surface, we show that a band gap in the density
of states opens, reaching an effective value of ~sim50 meV. This demonstrates
the potential of bilayer graphene as FET channel material in a conventional
CMOS environment. | 1001.5213v1 |
2010-01-30 | Magnetoresistance of a spin MOSFET with ferromagnetic MnAs source and drain contacts | Spin-dependent transport was investigated in a spin metal-oxide-semiconductor
field-effect transistors (spin MOSFET) with ferromagnetic MnAs source and drain
(S/D) contacts. The spin MOSFET of bottom-gate type was fabricated by
photolithography using an epitaxial MnAs film grown on a silicon-on-insulator
(SOI) substrate. In-plane magnetoresistance showed spin-valve-type hysteretic
behavior, when the measurements were performed with constant source-drain and
source-gate biases. By comparing with the magnetization-related resistance
change resulting from the MnAs contacts, we conclude that the spin-polarized
electrons are injected from the MnAs source into the Si MOS inversion channel,
and detected by the MnAs drain. | 1002.0057v1 |
2010-02-03 | Dislocation Mobility in a Quantum Crystal: the Case of Solid 4He | We investigate the structure and mobility of dislocations in hcp 4He
crystals. In addition to fully characterizing the five elastic constants of
this system, we obtain direct insight into dislocation core structures on the
basal plane, which demonstrates a tendency toward dissociation into partial
dislocations. Moreover, our results suggest that intrinsic lattice resistance
is an essential factor in the mobility of these dislocations. This insight
sheds new light on the possible correlation between dislocation mobility and
the observed macroscopic behavior of crystalline 4He. | 1002.0704v1 |
2010-03-15 | Electron localization near Mott transition in organic superconductor $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}]$Br | The effect of disorder on the electronic properties near the Mott transition
is studied in an organic superconductor
$\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br, which is systematically irradiated
by X-ray. We observe that X-ray irradiation causes Anderson-type electron
localization due to molecular disorder. The resistivity at low temperatures
demonstrates variable range hopping conduction with Coulomb interaction. The
experimental results show clearly that the electron localization by disorder is
enhanced by the Coulomb interaction near the Mott transition. | 1003.2890v2 |
2010-03-25 | Columnar Fluctuations as a Source of Non-Fermi-Liquid Behavior in Weak Metallic Magnets | It is shown that columnar fluctuations, in conjunction with weak quenched
disorder, lead to a T^{3/2} temperature dependence of the electrical
resistivity. This is proposed as an explanation of the observed
non-Fermi-liquid behavior in the helimagnet MnSi, with one possible realization
of the columnar fluctuations provided by skyrmion lines that have independently
been proposed to be present in this material. | 1003.4809v3 |
2010-03-28 | Giant magnetic broadening of ferromagnetic resonance in a GMR Co/Ag/Co/Gd quadlayer | Both magnetic-resonance damping and the giant magnetoresistance effect have
been predicted to be strongly affected by the local density of states in thin
ferromagnetic films. We employ the antiferromagnetic coupling between Co and Gd
to provide a spontaneous change from parallel to antiparallel alignment of two
Co films. A sharp increase in magnetic damping accompanies the change from
parallel to antiparallel alignment, analogous to resistivity changes in giant
magnetoresistance. | 1003.5344v1 |
2010-04-05 | Non-monotonic variation of anomalous Hall effect with spin orbit coupling strength | For L1(0) FePt films, the anomalous Hall resistivity is found to be
proportional to spontaneous magnetization $M_{\mathrm{S}}$. After the
$M_{\mathrm{S}}$ temperature effect is eliminated, $\rho_{\mathrm{xyo}}$ can be
fitted by $\rho_{\mathrm{xyo}}=a_{\mathrm{o}}\rho_{\mathrm{xx}}+
b_{\mathrm{o}}\rho_{\mathrm{xx}}^{\mathrm{2}}$. $a_{\mathrm{o}}$ and
$b_{\mathrm{o}}$ change non-monotonically with chemical long range ordering
degree $S$. Accordingly, it is indicated that for L1(0) FePt films the spin
orbit coupling strength increases monotonically with increasing $S$. | 1004.0548v4 |
2010-04-29 | Designing multifunctional chemical sensors using Ni and Cu doped carbon nanotubes | We demonstrate a "bottom up" approach to the computational design of a
multifunctional chemical sensor. General techniques are employed for describing
the adsorption coverage and resistance properties of the sensor based on
density functional theory (DFT) and non-equilibrium Green's function
methodologies (NEGF), respectively. Specifically, we show how Ni and Cu doped
metallic (6,6) single-walled carbon nanotubes (SWNTs) may work as effective
multifunctional sensors for both CO and NH3. | 1004.5334v1 |
2010-05-19 | Electron properties of fluorinated single-layer graphene transistors | We have fabricated transistor structures using fluorinated single-layer
graphene flakes and studied their electronic properties at different
temperatures. Compared with pristine graphene, fluorinated graphene has very
large and strongly temperature dependent resistance in the electro-neutrality
region. We show that fluorination creates a mobility gap in graphene's spectrum
where electron transport takes place via localised electron states. | 1005.3474v3 |
2010-06-22 | Hall carrier density and magnetoresistance measurements in thin film vanadium dioxide across the metal-insulator transition | Temperature dependent magneto-transport measurements in magnetic fields of up
to 12 Tesla were performed on thin film vanadium dioxide (VO2) across the
metal-insulator transition (MIT). The Hall carrier density increases by 4
orders of magnitude at the MIT and accounts almost entirely for the resistance
change. The Hall mobility varies little across the MIT and remains low,
~0.1cm2/V sec. Electrons are found to be the major carriers on both sides of
the MIT. Small positive magnetoresistance in the semiconducting phase is
measured. | 1006.4376v1 |
2010-08-15 | Limits on electron quality in suspended graphene due to flexural phonons | The temperature dependence of the mobility in suspended graphene samples is
investigated. In clean samples, flexural phonons become the leading scattering
mechanism at temperature $T \gtrsim 10\,\,$K, and the resistivity increases
quadratically with $T$. Flexural phonons limit the intrinsic mobility down to a
few $\text{m}^2/\text{Vs}$ at room $T$. Their effect can be eliminated by
applying strain or placing graphene on a substrate. | 1008.2522v1 |
2010-08-29 | Shubnikov-de Haas oscillations in SrTiO3\LaAlO3 interface | Quantum magnetic oscillations in SrTiO3/\LaAlO3 interface are observed. The
evolution of their frequency and amplitude at various gate voltages and
temperatures is studied. The data are consistent with the Shubnikov de-Haas
theory. The Hall resistivity rho exhibits nonlinearity at low magnetic field.
It is fitted assuming multiple carrier contributions. The comparison between
the mobile carrier density inferred from the Hall data and the oscillation
frequency suggests multiple valley and spin degeneracy. The small amplitude of
the oscillations is discussed in the framework of the multiple band scenario. | 1008.4975v1 |
2010-09-01 | Two distinct quasiparticle inelastic scattering rates in the $t-J$ model and their relevance for high-$T_c$ cuprates superconductors | The recent findings about two distinct quasiparticle inelastic scattering
rates in angle-dependent magnetoresistance (ADMR) experiments in overdoped
high-$T_c$ cuprates superconductors have motivated many discussions related to
the link between superconductivity, pseudogap, and transport properties in
these materials. After computing dynamical self-energy corrections in the
framework of the $t-J$ model the inelastic scattering rate was introduced as
usual. Two distinct scattering rates were obtained showing the main features
observed in ADMR experiments. Predictions for underdoped cuprates are
discussed. The implicances of these two scattering rates on the resistivity
were also studied as a function of doping and temperature and confronted with
experimental measurements. | 1009.0158v1 |
2010-10-15 | Theory of I-V Characteristics of Magnetic Josephson Junctions | We analyze the electrical characteristics of a circuit consisting of a free
thin-film magnetic layer and source and drain electrodes that have opposite
magnetization orientations along the free magnet's two hard directions. We find
that when the circuit's current exceeds a critical value there is a sudden
resistance increase which can be large in relative terms if the currents to
source or drain are strongly spin polarized and the free magnet is thin. This
behavior can be partly understood in terms of a close analogy between the
magnetic circuit and a Josephson junction. | 1010.3073v1 |
2010-10-29 | The Structural and Magnetic ordering in $La{}_{0.5-x}Nd_{x}Ca_{0.5}MnO_{3}$ (0.1 \ensuremath{\le} x \ensuremath{\le} 0.5) Manganites | The crystal and magnetic structure of polycrystalline
$La{}_{0.5-x}Nd{}_{x}Ca_{0.5}MnO{}_{3}$ (0.0 \ensuremath{\le} x
\ensuremath{\le} 0.5) samples have been investigated using magnetization,
resistivity, transmission electron microscope, and neutron diffraction
techniques. The samples are isostructural and possess orthorhombic structure in
\textit{Pnma} space group. On lowering of temperature, the samples exhibit CE -
type antiferromagnetic structure coexisting with a weak ferromagnetic ordering.
The charge and orbitally ordered antiferromagnetic phase is weakened by the
growth of ferromagnetic phase. The evolution of structural distortions and
magnetic structure at low temperature as a function of Nd doping exhibit a
strong correlation with A - site disorder ($\sigma{}^{2}$). | 1010.6124v1 |
2010-12-15 | Giant Tunneling Electroresistance Effect Driven by an Electrically Controlled Spin Valve at a Complex Oxide Interface | A giant tunneling electroresistance effect may be achieved in a ferroelectric
tunnel junction by exploiting the magnetoelectric effect at the interface
between a ferroelectric barrier and magnetic La1-xSrxMnO3 electrode. Using
first-principles density functional theory we demonstrate that a few magnetic
monolayers of La1-xSrxMnO3 near the interface act, in response to ferroelectric
polarization reversal, as an atomic scale spin-valve by filtering
spin-dependent current. This effect produces more than an order of magnitude
change in conductance, and thus constitutes a giant resistive switching effect. | 1012.3421v2 |
2010-12-17 | Electro thermal simulation of superconducting nanowire avalanche photodetectors | We developed an electro thermal model of NbN superconducting nanowire
avalanche photodetectors (SNAPs) on sapphire substrates. SNAPs are single
photon detectors consisting of the parallel connection of N superconducting
nanowires. We extrapolated the physical constants of the model from
experimental data and we simulated the time evolution of the device resistance,
temperature and current by solving two coupled electrical and thermal
differential equations describing the nanowires. The predictions of the model
were in good quantitative agreement with the experimental results. | 1012.3964v1 |
2010-12-17 | Ternary Tetradymite Compounds as Topological Insulators | Ternary tetradymites Bi2Te2S, Bi2Te2Se and Bi2Se2Te are found to be stable,
bulk topological insulators via theory, showing band inversion between group V
and VI pz orbitals. We identify Bi2Se2Te as a good candidate to study massive
Dirac Fermions, with a (111) cleavage-surface-derived Dirac point (DP) isolated
in the bulk band gap at the Fermi energy Ef like Bi2Se3 but with a spin texture
alterable by layer chemistry. In contrast, Bi2Te2S and Bi2Te2Se (111) behave
like Bi2Te3, with a DP below Ef buried in bulk bands. Bi2Te2S offers large bulk
resistivity needed for devices. | 1012.3974v3 |
2011-01-18 | Metal-insulator transition and electrically-driven memristive characteristics of SmNiO3 thin films | The correlated oxide SmNiO3 (SNO) exhibits an insulator to metal transition
(MIT) at 130 {\deg}C in bulk form. We report on synthesis and electron
transport in SNO films deposited on LaAlO3 (LAO) and Si single crystals. X-ray
diffraction studies show that compressively strained single-phase SNO grows
epitaxially on LAO while on Si, mixed oxide phases are observed. MIT is
observed in resistance-temperature measurements in films grown on both
substrates, with charge transport in-plane for LAO/SNO films and out-of-plane
for Si/SNO films. Electrically-driven memristive behavior is realized in
LAO/SNO films, suggesting that SNO may be relevant for neuromorphic devices. | 1101.3538v1 |
2011-01-25 | Ferron Type of Coductivity in Metal CuFeSe2 | It is pointed out, that the charge transfer in the compound in paramagnetic
region has a ferron type of transport with ferrons of a small radius, predicted
by N. Mott. For some another specimen the charge transfer may be carried out by
ferrons of a large radius at very low temperatures. The results are well
confirmed by the temperature dependence of resistivity and by metal type of the
compound. | 1101.4904v2 |
2011-02-04 | Anisotropy in transport and magnetic properties of K0.64Fe1.44Se2 | We report a study of anisotropy in transport and magnetic properties of
K0.64Fe1.44Se2.00 single crystals. The anisotropy in resistivity is up to one
order of magnitude between 1.8 K and 300 K. Magnetic susceptibility exhibits
weak temperature dependence in the normal state with decrease in temperature
with no significant anomalies. The lower critical fields Hc1 of
K0.64Fe1.44Se2.00 are only about 3 Oe and the anisotropy of Hc1,c/Hc1,ab is
about 1. The critical currents for H||ab and H||c are about 10-10^3 A/cm2,
smaller than in iron pnictides and in FeTe_{1-x}Se_{x} and nearly isotropic. | 1102.1010v3 |
2011-03-01 | Experimental Spin Ratchet | Spintronics relies on the ability to transport and utilize the spin
properties of an electron rather than its charge. We describe a spin rachet at
the single-electron level that produces spin currents with no net bias or
charge transport. Our device is based on the ground state energetics of a
single electron transistor comprising a superconducting island connected to
normal leads via tunnel barriers with different resistances that break spatial
symmetry. We demonstrate spin transport and quantify the spin ratchet
efficiency using ferromagnetic leads with known spin polarization. Our results
are modeled theoretically and provide a robust route to the generation and
manipulation of pure spin currents. | 1103.0105v1 |
2011-03-15 | Quantum transport in oxide nanostructures | We describe magnetotransport experiments performed on Hall crosses made from
quantum wires at LaAlO3/SrTiO3 interfaces. Shubnikov-de Haas oscillations
measured in a 14-nm wide structure exhibit modulations that are consistent with
spin-orbit coupling or valley degeneracies. Hall measurements performed on the
6 nm-wide Hall cross reveal dissipative coupling to magnetic phases. Hall
plateaus are observed that deviate significantly from two-dimensional quantum
Hall counterparts. Non-monotonic dips in the Hall resistance are attributed to
one-dimensional confinement and spin-orbit coupling. | 1103.3036v1 |
2011-03-29 | Atomistic calculation of the thermal conductance of large scale bulk-nanowire junctions | We have developed an efficient scalable kernel method for thermal transport
in open systems, with which we have computed the thermal conductance of a
junction between bulk silicon and silicon nanowires with diameter up to 10 nm.
We have devised scaling laws for transmission and reflection spectra, which
allow us to predict the thermal resistance of bulk-nanowire interfaces with
larger cross sections than those achievable with atomistic simulations. Our
results indicate the characteristic size beyond which atomistic systems can be
treated accurately by mesoscopic theories. | 1103.5581v1 |
2011-03-30 | Anomalous conductivity dependence of plasticized PVC for different modificator "A" concentrations and film thicknesses | The dependences of electrical conductivity of plasticized PVC films on mass
fraction of plasticizer "A" and the film thickness are experimentally
investigated. Non-monotonic dependence of conductivity on the concentration of
plasticizer and strongly nonlinear dependence of the resistance of the film on
its thickness are found. Possibility of construction of the models describing
received results is shown and also discussed. | 1103.5975v1 |
2011-05-12 | Coulomb drag in graphene single layers separated by a thin spacer | Motivated by very recent studies of Coulomb drag in grahene-BN-graphene
system we develop a theory of Coulomb drag for the Fermi liquid regime, for the
case when the ratio of spacer thickness $d$ to the Fermi wavelength of
electrons is arbitrary. The concentration ($n$) and thickness dependence of the
drag resistivity is changed from $n^{-3}d^{-4}$ for the thick spacer to
$n^{-1}|\ln{(nd^2)}|$ for the thin one. | 1105.2534v2 |
2011-05-30 | A ferromagnetic-like phase transition in new oxychalcogenide HgOCuSe | We report the synthesis of a new oxychalcogenide HgOCuSe sample. The
resistivity decreases as a function of $T^{1.75}$ with decreasing temperature
from room temperature down to around 80 K. There exists a very sharp
ferromagnetic-like phase transition at around 60 K under a field of $H$ = 100
Oe. Contrary to the usual ferromagnetic materials, the descending and ascending
branches of the magnetic hysteresis curve, at 30 K, are reversed in the whole
irreversible field range and the reverse irreversibility decreases at 5 K. | 1105.5868v1 |
2011-06-20 | A fully woven touchpad sensor based on soft capacitor fibers | A novel, highly flexible capacitor fiber (with 100 nF m-1 typical capacitance
per length) having a multilayer periodic structure of dielectric and conductive
polymer composite films is fabricated by drawing technique. The fiber is used
to build a woven touchpad sensor. Then, we study the influence of the fiber
length, capacitance and volume resistivity on the touch sensing performance. A
theoretical ladder network model of a fiber network is developed. A fully woven
textile sample incorporating one-dimension array of the capacitor fibers is
fabricated. Finally we show that such an array functions as a two-dimensional
touch sensor. | 1106.3881v1 |
2011-06-24 | Coexistence of bulk superconductivity and charge density wave in CuxZrTe3 | We report coexistence of bulk superconductivity and charge density wave (CDW)
with superconducting critical temperature Tc = 3.8 K in Cu intercalated
quasi-two-dimensional crystals of ZrTe3. The Cu intercalation results in the
expansion of the unit cell orthogonal to the Zr-Zr metal chains (b - axis) and
partial filling of CDW energy bandgap without obvious shift of CDW transition
temperature. b - axis resistivity ?Rhob is not related to CDW, and its dominant
scattering mechanism for both ZrTe3 and Cu0.05ZrTe3 is the electron - electron
Umklapp scattering. | 1106.5047v1 |
2011-08-01 | Enhancement of Spin Injection into Graphene by Water Dipping | We immerse single layer graphene spin valves into purified water for a short
duration (<1 min) and investigate the effect on spin transport. Following water
immersion, we observe an enhancement in nonlocal magnetoresistance.
Additionally, the enhancement of spin signal is correlated with an increase in
junction resistance, which produces an increase in spin injection efficiency.
This study provides a simple way to improve the signal magnitude and
establishes the robustness of graphene spin valves to water exposure, which
enables future studies involving chemical functionalization in aqueous
solution. | 1108.0380v1 |
2011-08-12 | Magnetic noise induced by dc current in a micron-size magnetic wire | The magnetic noise spectra induced by direct-current (dc) current flowing
through a micron-scale ferromagnetic wire have been investigated. We have
observed the noise spectra with a resonance frequency. Under the application of
the magnetic field in the plane, the magnetic field dependences of the
resonance frequency and amplitude were well interpreted by the analytical
calculation based on the stochastic model. The noise spectra are attributable
to the resistance oscillation reflecting the uniform magnetization precession
which is produced by the Joule heating due to the dc current. | 1108.2548v1 |
2011-09-29 | Sources of negative tunneling magneto-resistance in multilevel quantum dots with ferromagnetic contacts | We analyze distinct sources of spin-dependent energy level shifts and their
impact on the tunneling magnetoresistance (TMR) of interacting quantum dots
coupled to collinearly polarized ferromagnetic leads. Level shifts due to
virtual charge fluctuations can be quantitatively evaluated within a
diagrammatic representation of our transport theory. The theory is valid for
multilevel quantum dot systems and we exemplarily apply it to carbon nanotube
quantum dots, where we show that the presence of many levels can qualitatively
influence the TMR effect. | 1109.6599v1 |
2011-10-13 | Tuning the structural instability of SrTiO_3 by Eu doping: The phase diagram of Sr_1-xEu_xTiO_3 | The phase diagram of Sr_1-xEu_xTiO_3 is determined experimentally by electron
paramagnetic resonance and resistivity measurements and analyzed theoretically
within the self-consistent phonon approximation as a function of x
([0.03-1.0]). The transition temperature of the structural instability of the
system increases nonlinearly to higher temperatures with increasing x. This is
interpreted theoretically by a substantial alteration in the dynamics caused by
a change in the double-well potential from broad and shallow to narrow and
deep. | 1110.2922v2 |
2011-11-21 | Ink-Jet Printed Graphene Electronics | We demonstrate ink-jet printing as a viable method for large area fabrication
of graphene devices. We produce a graphene-based ink by liquid phase
exfoliation of graphite in N-Methylpyrrolidone. We use it to print thin-film
transistors, with mobilities up to~95cm^2V^(-1)s(-1), as well as transparent
and conductive patterns, with~80 % transmittance and~30kOhm/sq sheet
resistance. This paves the way to all-printed, flexible and transparent
graphene devices on arbitrary substrates | 1111.4970v1 |
2011-11-24 | Domain wall attraction and repulsion during spin-torque-induced coherent motion | We calculate the interaction between two magnetic domain walls during their
current-induced motion. This interaction produces a separation-dependent
resistance and also a differential velocity, causing domains in motion to
experience an effective attraction at large separations and an effective
repulsion at short separations. In an intermediate range of currents the two
domain walls will reach a natural equilibrium spacing that depends on the
magnitude of the current flowing through the material. | 1111.5868v1 |
2011-12-09 | Characterization and Predictive Modeling of Epitaxial Silicon-Germanium Thermistor Layers | The thermal coefficient of resistance (TCR) for epitaxial silicon-germanium
(SiGe) layers has been analyzed by experiment and simulation. Predictive
simulation using drift-diffusion formalism and self-consistent
quantum-mechanical solutions yielded similar results, TCR around 2%/K at 300 K.
This modeling approach can be used for different, graded and constant, SiGe
profiles,. It is also capable of predicting the influence of background
auto-doping on the TCR of the detectors | 1112.2043v1 |
2011-12-14 | Possibility of a zero-temperature metallic phase in granular two-band superconducting films | A variational approach is used to study the superconductor-insulator
transition in two-band granular superconducting films using a
resistance-shunted Josephson junction array model in this letter. We show that
a zero-temperature metallic phase may exist between the superconducting and
insulator phases which is absent in normal single band granular superconducting
films. The metallic phase may be observable in some dirty pnictide
superconductor films. | 1112.3132v2 |
2012-02-08 | Seismic Waveguide of Metamaterials | We have developed a new method of an earthquake-resistant design to support
conventional aseismic designs using acoustic metamaterials. We suggest a simple
and practical method to reduce the amplitude of a seismic wave exponentially.
Our device is an attenuator of a seismic wave. Constructing a cylindrical
shell-type waveguide that creates a stop-band for the seismic wave, we convert
the wave into an evanescent wave for some frequency range without touching the
building we want to protect. | 1202.1586v1 |
2012-04-10 | Modeling the underlying mechanisms for organic memory devices: Tunneling, electron emission and oxygen adsorbing | We present a combined experimental and theoretical study to get insight into
both memory and negative differential resistance (NDR) effect in organic memory
devices. The theoretical model we propose is simply a one-dimensional metallic
island array embedding within two electrodes. We use scattering operator method
to evaluate the tunneling current among the electrode and islands to establish
the basic bistable I-V curves for several devices. The theoretical results
match the experiments very well, and both memory and NDR effect could be
understood comprehensively. The experimental correspondence, say, the
experiment of changing the pressure of oxygen, is addressed as well. | 1204.2022v1 |
2012-04-18 | Magnetoresistance Relaxation in (La0.5Eu0.5)0.7Pb0.3MnO3 Single Crystals under the Action of a Pulse Magnetic Field | Magnetoresistance of substituted lanthanum manganite (La0.5Eu0.5)0.7Pb0.3MnO3
in the pulse magnetic field H = 25 T was measured at different temperatures.
Magnetoresistance relaxation with a characteristic time of 10 -3 s was found.
It has been established that the temperature dependence of the relaxation
parameter {\tau}(t) at different temperatures correlates with the temperature
dependence of electrical resistance R(T). The proposed relaxation mechanism is
related to relaxation of conducting and dielectric phases in the sample volume
under phase stratification conditions. It is shown that relaxation parameter
{\tau} reflects the number of boundaries in the volume and not the ratio
between phase fractions. | 1204.3987v1 |
2012-05-18 | Metal-to-insulator transition in anatase TiO2 thin films induced by growth rate modulation | We demonstrate control of the carrier density of single phase anatase TiO2
thin films by nearly two orders of magnitude by modulating the growth kinetics
during pulsed laser deposition, under fixed thermodynamic conditions. The
resistivity and the intensity of the photoluminescence spectra of these TiO2
samples, both of which correlate with the number of oxygen vacancies, are shown
to depend strongly on the growth rate. A quantitative model is used to explain
the carrier density changes. | 1205.4065v1 |
2012-05-30 | Type-I superconductivity in ScGa3 and LuGa3 single crystals | We present evidence of type-I superconductivity in single crystals of ScGa3
and LuGa3, from magnetization, specific heat, and resistivity measurements: low
critical temperatures Tc = 2.1-2.2 K; field-induced secondto first-order phase
transition in the specific heat, critical fields less than 240 Oe; and low
Ginzburg-Landau coefficients {\kappa} approx 0.23 and 0.30 for ScGa3 and LuGa3,
respectively, are all traits of a type-I superconducting ground state. These
observations render ScGa3 and LuGa3 two of only several type-I superconducting
compounds, with most other superconductors being type II (compounds and alloys)
or type I (elemental metals and metaloids). | 1205.6836v1 |
2012-07-20 | Superconducting state in the metastable binary bismuthide Rh3Bi14 single crystals | We report detailed magnetic, transport and thermodynamic properties of
metastable Rh3Bi14 single crystals in superconducting and normal state. We show
that Rh3Bi14 is nearly isotropic, weak to intermediately coupled BCS
superconductor, whereas the electronic resistivity above superconducting Tc =
2.94 K is dominated by the phonon scattering in the large unit cell with pores
filled by Bi atoms. Superconductivity is strongly influenced by the nature of
atoms that fill the voids in the crystal structure. | 1207.5043v1 |
2012-08-23 | Evolution of c-f hybridization and two component Hall effect in β-YbAlB_4 | \beta-YbAlB_4 is the unique heavy fermion superconductor that exhibits
unconventional quantum criticality without tuning in a strongly intermediate
valence state. Despite the large coherence temperature, set by the peak of the
longitudinal resistivity, our Hall effect measurements reveal that resonant
skew scattering from incoherent local moments persists down to at least ~40 K,
where the Hall coefficient exhibits a distinct minimum signaling another
formation of coherence. The observation strongly suggests that the
hybridization between f-moments and conduction electrons has a two component
character with distinct Kondo or coherence scales T_K of ~40 K and 200 K; this
is confirmed by the magnetic field dependence of \rho_xy. | 1208.4680v1 |
2012-08-28 | Trench Gate Power MOSFET: Recent Advances and Innovations | The trench gate MOSFET has established itself as the most suitable power
device for low to medium power applications by offering the lowest possible ON
resistance among all MOS devices. The evolution of the trench gate power MOSFET
has been discussed in this chapter, starting right from its beginnings to the
recent trends. The innovations in the structural improvements to meet the
requirements for an efficient operation, the progress in the fabrication
technology, the characterization methods and various reliability issues have
been emphasized. | 1208.5553v1 |
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