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7,000 | Transport and Boundary Scattering in Confined Geometries: Analytical Results | cond-mat.supr-con | We utilize a geometric argument to determine the effects of boundary
scattering on the carrier mean-free path in samples of various cross sections.
Analytic expressions for samples with rectangular and circular cross sections
are obtained. We also outline a method for incorporating these results into
calculations of th... | physics |
7,001 | Quantum Interference on the Kagomé Lattice | cond-mat.supr-con | We study quantum interference effects due to electron motion on the Kagom\'e
lattice in a perpendicular magnetic field. These effects arise from the
interference between phase factors associated with different electron
closed-paths. From these we compute, analytically and numerically, the
superconducting-normal phase b... | physics |
7,002 | Theory of Scanning Tunneling Microscopy Probe of Impurity States in a D-Wave Superconductor | cond-mat.supr-con | Scanning tunneling microscopy can provide a probe for the detailed study of
quasiparticle states in high-Tc superconductors. We propose that it can also be
used to acquire specific information about impurity-induced quasiparticle
states and the superconducting order-parameter structure. In particular, the
local density... | physics |
7,003 | Effects of Interlayer Interaction on the Superconducting State in YBCO | cond-mat.supr-con | For a two layer system in a weak coupling BCS formalism any interlayer
interaction, regardless of its sign, enhances the critical temperature. The
sign has an effect upon the relative phase of the order parameter in each of
the two planes but not upon its magnitude. When one of the planes has a
dispersion consistent wi... | physics |
7,004 | Superfluid Bosons and Flux Liquids: Disorder, Thermal Fluctuations, and Finite-Size Effects | cond-mat.supr-con | The influence of different types of disorder (both uncorrelated and
correlated) on the superfluid properties of a weakly interacting or dilute Bose
gas, as well as on the corresponding quantities for flux line liquids in
high-temperature superconductors at low magnetic fields are reviewed,
investigated and compared. We... | physics |
7,005 | Similarity renormalization of the electron--phonon coupling | cond-mat.supr-con | We study the problem of the phonon-induced electron-electron interaction in a
solid. Starting with a Hamiltonian that contains an electron-phonon
interaction, we perform a similarity renormalization transformation to
calculate an effective Hamiltonian. Using this transformation singularities due
to degeneracies are avo... | physics |
7,006 | High-T_c Superconductivity and Shadow State Formation in YBa_{2}Cu_{3}O_{6+δ} and Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} | cond-mat.supr-con | The normal and superconducting state of YBa_{2}Cu_{3}O_{6+\delta} and
Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} are investigated by using the mono- and
bilayer Hubbard model within the fluctuation exchange approximation and a
proper description of the Fermi surface topology. The inter- and intra-layer
interactions, the renormal... | physics |
7,007 | Simple Ginzburg-Landau Theory for Vortices in a Crystal Lattice | cond-mat.supr-con | We study the Ginzburg-Landau model with a nonlocal quartic term as a simple
phenomenological model for superconductors in the presence of coupling between
the vortex lattice and the underlying crystal lattice. In mean-field theory,
our model is consistent with a general oblique vortex lattice ranging from a
triangular ... | physics |
7,008 | First-Order Melting of a Moving Vortex Lattice: Effects of Disorder | cond-mat.supr-con | We study the melting of a moving vortex lattice through numerical simulations
with the current driven 3D XY model with disorder. We find that there is a
first-order phase transition even for large disorder when the corresponding
equilibrium transition is continuous. The low temperature phase is an
anisotropic moving gl... | physics |
7,009 | Generalized London free energy for high-$T_c$ vortex lattices | cond-mat.supr-con | We generalize the London free energy to include four-fold anisotropies which
could arise from d-wave pairing or other sources in a tetragonal material. We
use this simple model to study vortex lattice structure and discuss neutron
scattering, STM, Bitter decoration and $\mu$SR experiments. | physics |
7,010 | Mean field analysis of a model for superconductivity in an antiferromagnetic background | cond-mat.supr-con | We study a lattice fermion model for superconductivity in the presence of an
antiferromagnetic background, described as a fixed external staggered magnetic
field. We discuss the possibility that our model provides an effective
description of coexistence of antiferromagnetic correlations and
superconductivity, and its p... | physics |
7,011 | New features in the microwave response of YBCO crystals: Evidence for a multi-component order parameter | cond-mat.supr-con | New features are reported in precision measurements of the complex microwave
conductivity of high quality $YBa_{2}Cu_{3}O_{6.95}$ crystals grown in
$BaZrO_{3}$ crucibles. A third peak in the normal conductivity,
$\sigma_{1}(T)$, at around $80K$, and enhanced pair conductivity
$\sigma_{2}(T)$ below $\sim 65K$ are observ... | physics |
7,012 | Unconventional Pairing in Heavy Fermion Metals | cond-mat.supr-con | The Fermi-liquid theory of superconductivity is applicable to a broad range
of systems that are candidates for unconventional pairing. Fundamental
differences between unconventional and conventional anisotropic superconductors
are illustrated by the unique effects that impurities have on the
low-temperature transport p... | physics |
7,013 | Flux penetration in slab shaped Type-I superconductors | cond-mat.supr-con | We study the problem of flux penetration into type--I superconductors with
high demagnetization factor (slab geometry).Assuming that the interface between
the normal and superconducting regions is sharp, that flux diffuses rapidly in
the normal regions, and that thermal effects are negligible, we analyze the
process by... | physics |
7,014 | Mutual influence of structural distortion and superconductivity in systems with degenerate bands | cond-mat.supr-con | The interplay between the band Jahn-Teller distortion and the
superconductivity is studied for the system whose Fermi level lies in two-fold
degenerate band. Assuming that the lattice distortion is coupled to the orbital
electron density and the superconductivity arises due to BCS pairing mechanism
between the electron... | physics |
7,015 | Critical properties of two-dimensional Josephson junction arrays with zero-point quantum fluctuations | cond-mat.supr-con | We present results from an extensive analytic and numerical study of a
two-dimensional model of a square array of ultrasmall Josephson junctions. We
include the ultrasmall self and mutual capacitances of the junctions, for the
same parameter ranges as those produced in the experiments. The model
Hamiltonian studied inc... | physics |
7,016 | Induction of non-d-wave order-parameter components by currents in d-wave superconductors | cond-mat.supr-con | It is shown, within the framework of the Ginzburg-Landau theory for a
superconductor with d_{x^2-y^2} symmetry, that the passing of a supercurrent
through the sample results, in general, in the induction of order-parameter
components of distinct symmetry. The induction of s-wave and
d_{xy(x^2-y^2)-wave components are c... | physics |
7,017 | Logarithmic divergence of normal state resistivity of bipolaronic high-$T_{c}$ cuprates | cond-mat.supr-con | The resonance Wigner scattering of charged bosons (small bipolarons) in a
random potential leads to logarithmically divergent low-temperature resistivity
as observed in several cuprates. Unusual temperature dependence of resistivity
of $La_{2-x}Sr_{x}CuO_{4}$ as well as of the Hall effect is quantitatively
described in... | physics |
7,018 | Singularity of the Vortex Density of States in d-wave Superconductors | cond-mat.supr-con | In d-wave superconductors, the electronic density of states (DOS) induced by
a vortex exhibits 1/|E| divergency at low energies. It is the result of gap
nodes in the excitations spectrum outside the vortex core. The heat capacity in
two regimes, (T/T_c)^2 >> B/B_{c2} and (T/T_c)^2 << B/B_{c2}, is discussed. | physics |
7,019 | Superconducting transition induced by columnar disorder in strong magnetic field | cond-mat.supr-con | The superconducting transition in presence of strong columnar disorder
parallel to the magnetic field is considered. A solvable model appropriate for
description of the broad crossover regime towards the true "glassy" critical
behavior is constructed, and the behavior of the thermodynamic quantities and
of the Edwards-... | physics |
7,020 | The Effects of d_{x^2-y^2}-d_{xy} Mixing on Vortex Structures and Magnetization | cond-mat.supr-con | The structure of an isolated single vortex and the vortex lattice, and the
magnetization in a $d$-wave superconductor are investigated within a
phenomenological Ginzburg-Landau (GL) model including the mixture of the
$d_{x^2-y^2}$-wave and $d_{xy}$-wave symmetry. The isolated single vortex
structure in a week magnetic ... | physics |
7,021 | Scattering theory of superconductive tunneling in quantum junctions | cond-mat.supr-con | We present a consistent theory of superconductive tunneling in single-mode
junctions within a scattering formulation of Bogoliubov-de Gennes quantum
mechanics. Both dc Josephson effect and dc quasiparticle transport in voltage
biased junctions are considered. Elastic quasiparticle scattering by the
junction determines ... | physics |
7,022 | d_{x^2-y^2} Pair Domain Walls | cond-mat.supr-con | Using the density matrix renormalization group, we study domain wall
structures in the t-J model at a hole doping of x=1/8. We find that the domain
walls are composed of d_{x^2-y^2} pairs and that the regions between the domain
walls have antiferromagnetic correlations that are pi phase shifted across a
domain wall. At... | physics |
7,023 | Hall Effect in the mixed state of moderately clean superconductors | cond-mat.supr-con | The Hall conductivity in the mixed state of a clean ($l \gg \xi_0$) type-II
s-wave superconductor is determined from a microscopic calculation within a
quasiclassical approximation. We find that below the superconducting transition
the contribution to the transverse conductivity due to dynamical fluctuations
of the ord... | physics |
7,024 | Finite Size and Current Effects on IV Characteristics of Josephson Junction Arrays | cond-mat.supr-con | The effects of finite size and of finite current on the current-voltage
characteristics of Josephson junction arrays is studied both theoretically and
by numerical simulations. The cross-over from non-linear to linear behavior at
low temperature is shown to be a finite size effect and the non-linear behavior
at higher ... | physics |
7,025 | Stability of Elastic Glass Phases in Random Field XY Magnets and Vortex Lattices in Type II Superconductors | cond-mat.supr-con | A description of a dislocation-free elastic glass phase in terms of domain
walls is developed and used as the basis of a renormalization group analysis of
the energetics of dislocation loops added to the system. It is found that even
after optimizing over possible paths of large dislocation loops, their energy
is still... | physics |
7,026 | Phase Transitions in a Model Anisotropic High Tc Superconductor | cond-mat.supr-con | We carry out simulations of the anisotropic uniformly frustrated 3D XY model,
as a model for vortex line fluctuations in high Tc superconductors. We compute
the phase diagram as a function of temperature and anisotropy, for a fixed
applied magnetic field. We find that superconducting coherence parallel to the
field per... | physics |
7,027 | Theory of Thermal Conductivity in YBa_2Cu_3O_{7-δ} | cond-mat.supr-con | We calculate the electronic thermal conductivity in a d-wave superconductor,
including both the effect of impurity scattering and inelastic scattering by
antiferromagnetic spin fluctuations. We analyze existing experiments,
particularly with regard to the question of the relative importance of
electronic and phononic c... | physics |
7,028 | Poisson Brackets Scheme for Vortex Dynamics in Superfluids and Superconductors and Effect of Band Structure of Crystal | cond-mat.supr-con | Poisson brackets for the Hamiltonian dynamics of vortices are discussed for 3
regimes, in which the dissipation can be neglected and the vortex dynamics is
reversible: (i) The superclean regime when the spectral flow is suppressed.
(ii) The regime when the fermions are pinned by crystal lattice. This includes
also the ... | physics |
7,029 | Critical temperature and superfluid density suppression in disordered high-$T_c$ cuprate superconductors | cond-mat.supr-con | We argue that the standard Abrikosov-Gorkov (AG) type theory of $T_c$ in
disordered $d$-wave superconductors breaks down in short coherence length
high-$T_c$ cuprates. Numerical calculations within the Bogoliubov-de Gennes
formalism demonstrate that the correct description of such systems must allow
for the spatial var... | physics |
7,030 | Self-consistent scattering description of transport in normal-superconductor structures | cond-mat.supr-con | We present a scattering description of transport in several
normal-superconductor structures. We show that the related requirements of
self-consistency and current conservation introduce qualitative changes in the
transport behavior when the current in the superconductor is not negligible.
The energy thresholds for qua... | physics |
7,031 | Boundary conditions for quasiclassical equations in the theory of superconductivity | cond-mat.supr-con | In this paper we derive effective boundary conditions connecting the
quasiclassical Green's function through tunnel barriers in superconducting -
normal hybrid (S-N or S-S') structures in the dirty limit. Our work extends
previous treatments confined to the small transparency limit. This is achieved
by an expansion in ... | physics |
7,032 | Spectral Properties of Quasiparticle Excitations Induced by Magnetic Moments in Superconductors | cond-mat.supr-con | The consequences of localized, classical magnetic moments in superconductors
are explored and their effect on the spectral properties of the intragap bound
states is studied. Above a critical moment, a localized quasiparticle
excitation in an s-wave superconductor is spontaneously created near a magnetic
impurity, indu... | physics |
7,033 | Superconductivity in the three-leg Hubbard ladder: a Quantum Monte Carlo study | cond-mat.supr-con | Quantum Monte Carlo method is used to look into the superconductivity in the
three-leg Hubbard ladder. The enhanced correlation for the pairing across the
central and edge chains, which has been predicted in the weak-coupling
renormalization as an effect of coexistence of gapful and gapless spin modes,
is here shown to... | physics |
7,034 | Flux noise in high-temperature superconductors | cond-mat.supr-con | Spontaneously created vortex-antivortex pairs are the predominant source of
flux noise in high-temperature superconductors. In principle, flux noise
measurements allow to check theoretical predictions for both the distribution
of vortex-pair sizes and for the vortex diffusivity. In this paper the
flux-noise power spect... | physics |
7,035 | Absence of Translational Ordering in Driven Vortex Lattices | cond-mat.supr-con | By using finite temperature molecular dynamics simulations, we consider the
question of the existence of dynamical ordering as a two dimensional vortex
lattice is driven through a random background potential. The shape of the
current-voltage(I-V) characteristics are qualitatively the same as those seen
in experiments o... | physics |
7,036 | Fluctuations in the Lattice Ginzburg-Landau model | cond-mat.supr-con | Temporarly withdrawn. Larger version of this review is currently in
preparation. | physics |
7,037 | Anomalous superconducting state gap size versus Tc behavior in underdoped Bi_2Sr_2Ca_1-xDy_xCu_2O_8+d | cond-mat.supr-con | We report angle-resolved photoemission spectroscopy measurements of the
excitation gap in underdoped superconducting thin films of
Bi_2Sr_2Ca_{1-x}Dy_xCu_2O_{8+d}. As Tc is reduced by a factor of 2 by
underdoping, the superconducting state gap \Delta does not fall proportionally,
but instead stays constant or increases... | physics |
7,038 | Doping dependent quasiparticle band structure in cuprate superconductors | cond-mat.supr-con | We present an exact diagonalization study of the single particle spectral
function in the so-called t-t'-t''-J model in 2D. As a key result, we find that
unlike the `pure' t-J model, hole doping leads to a major reconstruction of the
quasiparticle band structure near (pi,0): whereas for the undoped system the
quasipart... | physics |
7,039 | The effect of field tilting on the dynamics of vortices pinned by correlated disorder | cond-mat.supr-con | Low-temperature dynamics of flux lines in high temperature, type II,
superconductors in the presence of correlated disorder in the form of columnar
defects is discussed. The effect of tilting the applied magnetic field with
respect to the column's directions is considered, using the non-Hermitian
quantum mechanics tech... | physics |
7,040 | Properties of Phase transitions of a Higher Order | cond-mat.supr-con | The following is a thermodynamic analysis of a III order (and some aspects of
a IV order) phase transition. Such a transition can occur in a superconductor
if the normal state is a diamagnet. The equation for a phase boundary in an H-T
(H is the magnetic field, T, the temperature) plane is derived. by considering
two p... | physics |
7,041 | Memory function approach to the Hall constant in strongly correlated electron systems: Part II | cond-mat.supr-con | The anomalous frequency and doping dependence of the Hall constant in the
normal state of high-T_c superconductors are investigated within models of
strongly correlated electron systems. In Mori theory, the transition of the
Hall constant from infinite to zero frequency is described by a memory
function. It naturally i... | physics |
7,042 | Angular position of nodes in the superconducting gap of YBCO | cond-mat.supr-con | The thermal conductivity of a YBCO single crystal has been studied as a
function of the relative orientation of the crystal axes and a magnetic field
rotating in the Cu-O planes. Measurements were carried out at several
temperatures below T_c and at a fixed field of 30 kOe. A four-fold symmetry
characteristic of a supe... | physics |
7,043 | Fractional vortices on grain boundaries --- the case for broken time reversal symmetry in high temperature superconductors | cond-mat.supr-con | We discuss the problem of broken time reversal symmetry near grain boundaries
in a d-wave superconductor based on a Ginzburg-Landau theory. It is shown that
such a state can lead to fractional vortices on the grain boundary. Both
analytical and numerical results show the structure of this type of state. | physics |
7,044 | Pseudogap State in High-$T_c$ Superconductors: an Infrared Study | cond-mat.supr-con | We report on a study of the electromagnetic response of three different
families of high-T_c superconductors that in combination allowed us to cover
the whole doping range from under- to overdoped. The discussion is focused on
the ab-plane charge dynamics in the {\it pseudogap state} which is realized in
underdoped mat... | physics |
7,045 | Vortex Quantum Nucleation and Tunneling in Superconducting Thin Films: Role of Dissipation and Periodic Pinning | cond-mat.supr-con | We investigate the phenomenon of decay of a supercurrent in a superconducting
thin film in the absence of an applied magnetic field. The resulting
zero-temperature resistance derives from two equally possible mechanisms: 1)
quantum tunneling of vortices from the edges of the sample; and 2) homogeneous
quantum nucleatio... | physics |
7,046 | Magnetic Dynamics in Underdoped YBCO: Direct Observation of a Superconducting Gap | cond-mat.supr-con | Polarized and unpolarized triple-axis spectrometry has been used to study an
underdoped YBa_2Cu3O6.6. Our results indicate that spin excitations in the
superconducting state are essentially the same as those in the fully doped
material except that the unusual 41 meV resonance is observed at 34.8 meV. The
normal state s... | physics |
7,047 | Scaling of the quasiparticle spectrum for d-wave superconductors | cond-mat.supr-con | In finite magnetic field H, the excitation spectrum of the low energy
quasiparticles in a 2 dimensional d-wave superconductor exhibits a scaling with
respect to $H^{1/2}$. This property can be used to calculate scaling relations
for various physical quantities at low temperature T. As examples, we make
predictions for ... | physics |
7,048 | Strong coupling theory of impure superconductors : real space formalism | cond-mat.supr-con | In the electron-phonon model, the influence of nonmagnetic impurities on the
transition temperature of superconductors is revisited. Anderson's pairing
condition between time-reversed eigenstate pairs is derived from the physical
constraint of the Anomalous Green's function. After this pairing condition is
incorporated... | physics |
7,049 | Random Matrix Model for Superconductors in a Magnetic Field | cond-mat.supr-con | We introduce a random matrix ensemble for bulk type-II superconductors in the
mixed state and determine the single-particle excitation spectrum using random
matrix theory. The results are compared with planar tunnel junction experiments
in PbBi thin films. More low energy states appear than in the
Abrikosov-Gor'kov-Mak... | physics |
7,050 | Superconductivity in Fullerides | cond-mat.supr-con | Experimental studies of superconductivity properties of fullerides are
briefly reviewed. Theoretical calculations of the electron-phonon coupling, in
particular for the intramolecular phonons, are discussed extensively. The
calculations are compared with coupling constants deduced from a number of
different experimenta... | physics |
7,051 | Generalized Ginzburg-Landau theory for non-uniform FFLO superconductors | cond-mat.supr-con | We derive a generalized Ginzburg-Landau (GL) functional near the tricritical
point in the (T,H)-phase diagram for the Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) superconducting state, in 1,2, and 3 dimensions. We find that the
transition from the normal to the FFLO state is of second order in 1 and 2
dimensions, and the o... | physics |
7,052 | Local density of states in the vortex lattice in a type II superconductor | cond-mat.supr-con | Local density of states (LDOS) in the triangular vortex lattice is
investigated based on the quasi-classical Eilenberger theory. We consider the
case of an isotropic s-wave superconductor with the material parameter
appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the
LDOS shows cylindrical str... | physics |
7,053 | Critical Fields of mesoscopic superconductors | cond-mat.supr-con | Recent measurements have shown oscillations in the upper critical field of
simply connected mesoscopic superconductors. A quantitative theory of these
effects is given here on the basis of a Ginzburg-Landau description. For small
fields, the $H-T$ phase boundary exhibits a cusp where the screening currents
change sign ... | physics |
7,054 | A Comparison of the High-Frequency Magnetic Fluctuations in Insulating and Superconducting La2-xSrxCuO4 | cond-mat.supr-con | Inelastic neutron scattering performed at a spallation source is used to make
absolute measurements of the dynamic susceptibility of insulating La2CuO4 and
superconducting La2-xSrxCuO4 over the energy range 15<EN<350 meV. The effect of
Sr doping on the magnetic excitations is to cause a large broadening in
wavevector a... | physics |
7,055 | Superconductivity Suppression Close to the Metal-Insulator Transition in Strongly Disordered Systems | cond-mat.supr-con | On the basis of the recently proposed self-consistent theory of metal-
insulator transition in strongly disordered systems, taking into account
interaction effects, we study transition temperature $T_{c}$ suppression in
disordered superconductors for the wide disorder interval --- from weakly
disordered metal up to And... | physics |
7,056 | Evolution of the Fermi surface with carrier concentration in Bi_2Sr_2CaCu_2O_{8+δ} | cond-mat.supr-con | We show, by use of angle-resolved photoemission spectroscopy, that underdoped
Bi_2Sr_2CaCu_2O_{8+\delta} appears to have a large Fermi surface centered at
(\pi,\pi), even for samples with a T_c as low as 15 K. No clear evidence of a
Fermi surface pocket around (\pi/2,\pi/2) has been found. These conclusions are
based o... | physics |
7,057 | Phonon Anomalies Induced by Superconductivity | cond-mat.supr-con | We calculate the electronic polarizability in the superconducting state near
extremum vectors ${\vec Q}_0$ of the Fermi surface. A pole appears in the
polarizability at frequencies $\omega$ near the superconducting gap $2\Delta$
which leads to a sharp peak at $\omega$ just below $2 \Delta$ in the lattice
vibrations nea... | physics |
7,058 | A Survey of the Van Hove Scenario for High-T_c Superconductivity With Special Emphasis on Pseudogaps and Striped Phases | cond-mat.supr-con | The Van Hove singularity (VHS) provides a paradigm for the study of the role
of peaks in the density of states (dos) on electronic properties. More
importantly, it appears to play a major role in the physics of the high-T_c
superconductors, particularly since recent photoemission studies have found
that the VHS is clos... | physics |
7,059 | Spin Dynamics in an Ordered Stripe Phase | cond-mat.supr-con | Inelastic neutron scattering has been used to measure the low-energy spin
excitations in the ordered charge-stripe phase of La(2)NiO(4+d) with d=0.133.
Spin-wave-like excitations disperse away from the incommensurate magnetic
superlattice points with a velocity ~60% of that in the d=0 compound.
Incommensurate inelastic... | physics |
7,060 | Slow antiferromagnetic dynamics in the low temperature tetragonal phase of La_{2-x}Sr_xCuO_4 as revealed by ESR of Gd spin probes | cond-mat.supr-con | Measuring the ESR of Gd spin probes we have studied the magnetic properties
of the copper oxide planes in the low temperature tetragonal (LTT) phase of Eu
doped La_{2-x}Sr_xCuO_4. The data give evidence that at particular levels of Sr
and Eu doping the frequency of the antiferromagnetic fluctuations in the LTT
phase dr... | physics |
7,061 | Vortices and 2D bosons: A Path-Integral Monte Carlo Study | cond-mat.supr-con | The vortex system in a high-T_c superconductor has been studied numerically
using the mapping to 2D bosons and the path-integral Monte Carlo method. We
find a single first-order transition from an Abrikosov lattice to an entangled
vortex liquid. The transition is characterized by an entropy jump dS = 0.4 k_B
per vortex... | physics |
7,062 | Bose glass and Mott insulator phase in the disordered boson Hubbard model | cond-mat.supr-con | We study the Villain representation of the two-dimensional disordered boson
Hubbard model via Monte Carlo simulations. It is shown that the probability
distribution of the local susceptibility has a 1/\chi^2-tail in the Bose glass
phase. This gives rise to a divergence although particles are completely
localized here a... | physics |
7,063 | The Critical Temperature of an Anisotropic Superconductor in the Presence of a Homogeneous Magnetic Field and Impurities | cond-mat.supr-con | The effect of a homogeneous magnetic field and nonmagnetic impurities on the
critical temperature of an anisotropic superconductor has been investigated.
The role of these pair-breakers in relation to the anisotropy of the order
parameter is clarified. | physics |
7,064 | Weak anisotropic impurity scattering in unconventional superconductors | cond-mat.supr-con | The effect of weak anisotropic (momentum-dependent) impurity scattering in
unconventional superconductors has been investigated. It is shown that the
anisotropic scattering can lead either to a small reduction or a small
enhancement of the isotropic pair-breaking effect. The influence of the
anisotropy of the scatterin... | physics |
7,065 | Anomalous vortex dynamics in 2D superconductors | cond-mat.supr-con | Low -frequency dynamic impedance
($\sigma^{-1}(\omega,T)\equiv(\sigma_{1}+i\sigma_{2})^{-1}$) measurements on
Josephson junction arrays with finite vortex screening length $\xi$, found that
$\sigma_{1}\sim |\log{\omega}|$, $\sigma_{2}\sim$ constant. This implies
anomalously sluggish vortex mobilities $\mu_{V}(\omega)\s... | physics |
7,066 | Nodes of the superconducting gap probed by electronic Raman scattering in HgBa_{2}CaCu_{2}O_{6+δ} single crystals | cond-mat.supr-con | Pure electronic Raman spectra with no phonon structures superimposed to the
electronic continuum, are reported, in optimally doped
HgBa_{2}CaCu_{2}O_{6+\delta } single crystals (T_{c }=126 K). As a consequence,
the spectra in the A_{1g }, B_{1g } and B_{2g } symmetries, including the
crucial low energy frequency depend... | physics |
7,067 | Effect of Interband Transitions on the c axis Penetration Depth of Layered Superconductors | cond-mat.supr-con | The electromagnetic response of a system with two planes per unit cell
involves, in addition to the usual intraband contribution, an added interband
term. These transitions affect the temperature dependence and the magnitude of
the zero temperature c-axis penetration depth. When the interplane hopping is
sufficiently s... | physics |
7,068 | Comment on Vortex Mass and Quantum Tunneling of Vortices | cond-mat.supr-con | Vortex mass in Fermi superfluids and superconductors and its influence on
quantum tunneling of vortices are discussed. The vortex mass is essentially
enhanced due to the fermion zero modes in the core of the vortex: the bound
states of the Bogoliubov qiasiparticles localized in the core. These bound
states form the nor... | physics |
7,069 | Plastic Flow, Voltage Bursts, and Vortex Avalanches in Superconductors | cond-mat.supr-con | We use large-scale parallel simulations to compute the motion of
superconducting magnetic vortices during avalanches triggered by small field
increases. We find that experimentally observable voltage bursts correspond to
pulsing vortex movement along branched channels or winding chains, and relate
vortex flow images to... | physics |
7,070 | Weakly Pinned Bose Glass vs. Mott Insulator Phase in Superconductors | cond-mat.supr-con | We study the properties of the Bose glass phase of localized flux lines in
irradiated superconductors near the matching field $B_{\Phi}$. Repulsive vortex
interactions destroy the Mott insulator phase predicted to occur at $B=B_\Phi$.
For ratios of the penetration depth to average defect distance $\lambda / d
\leq 1$ r... | physics |
7,071 | Triplanar Model for the Gap and Penetration Depth in YBCO | cond-mat.supr-con | YBaCuO_7 is a trilayer material with a unit cell consisting of a CuO_2
bilayer with a CuO plane of chains in between. Starting with a model of
isolated planes coupled through a transverse matrix element, we consider the
possibility of intra as well as interplane pairing within a nearly
antiferromagnetic Fermi liquid mo... | physics |
7,072 | Superconductivity-Induced Anomalies in the Spin Excitation Spectra of Underdoped YBa_2 Cu_3 O_{6+x} | cond-mat.supr-con | Polarized and unpolarized neutron scattering has been used to determine the
effect of superconductivity on the magnetic excitation spectra of YBa_2 Cu_3
O_{6.5} (T_c = 52K) and YBa_2 Cu_3 O_{6.7} (T_c = 67K). Pronounced enhancements
of the spectral weight centered around 25 meV and 33 meV, respectively, are
observed be... | physics |
7,073 | Evidence for strong electron-phonon coupling and polarons in the optical response of La_{2-x}Sr_xCuO_4 | cond-mat.supr-con | The normal state optical response of La_{2-x}Sr_xCuO_4 is found to be
consistent with a simple multi-component model, based on free carriers with
strong electron-phonon interaction, localized polaronic states near 0.15 eV and
a mid-infrared band at 0.5 eV. Normal state reflectance and absorbance of
La_{1.83}Sr_{0.17}Cu... | physics |
7,074 | Onset of Superfluidity in 4He Films Adsorbed on Disordered Substrates | cond-mat.supr-con | We have studied 4He films adsorbed in two porous glasses, aerogel and Vycor,
using high precision torsional oscillator and DC calorimetry techniques. Our
investigation focused on the onset of superfluidity at low temperatures as the
4He coverage is increased. Torsional oscillator measurements of the 4He-aerogel
system ... | physics |
7,075 | Ballistic Transport in Superconducting Weak Links in a Microwave Field | cond-mat.supr-con | Nonequilibrium effects and their impact on a charge transport in
superconducting ballistic weak links biased by an ac voltage are investigated
within the framework of the Keldysh technique. We demonstrate that the
microwave field destroys the phase coherence during the multiple Andreev
reflection cycle and leads to the... | physics |
7,076 | Design for the Detection of the Singly-Connected Superconducting State | cond-mat.supr-con | We study the Little-Parks effect for mesoscopic loops with very nonuniform
thickness. The results follow the trend of the phase diagram obtained for
almost uniform thickness. In particular, the singly-connected state is stable
on a line segment delimited by two critical points. Most of this study
considers loops with p... | physics |
7,077 | Plane - Chain coupling in YBa_{2}Cu_{3}O_{7} : temperature dependence of the penetration depth | cond-mat.supr-con | We have studied the penetration depth for a model of $YBa_{2}Cu_{3}O_{7}$
involving pairing both in the $CuO_{2}$ planes and in the CuO chains. In this
model pairing in the planes is due to an attractive interaction, while Coulomb
repulsion induces in the chains an order parameter with opposite sign. Due to
the anticro... | physics |
7,078 | Disorder Effects in Superconductors with Anisotropic Pairing: From Cooper Pairs to Compact Bosons | cond-mat.supr-con | In the weak coupling BCS-approximation normal impurities do not influence
superconducting T_{c} in significant manner in case of isotropic s-wave
pairing. However, in case of d-wave pairing these are strongly pair-breaking.
This fact is in rather strong contradiction with many experiments on disordered
high-T_{c} super... | physics |
7,079 | Why is d-wave pairing in HTS robust in the presence of impurities? | cond-mat.supr-con | In the recent theory of strong correlations by Kulic and Zeyher it has been
shown that by lowering doping concentration a forward peak in the charge
scattering channel is developed. Accordingly, near the optimal doping the
nonmagnetic scattering is pronounced in the d-channel and its effect on d-wave
pairing is reduced... | physics |
7,080 | Determination of the tunneling electron-phonon spectral function in high-Tc superconductors with energy dependence of the normal density of states | cond-mat.supr-con | We discuss the limits and the correct utilization of the standard program for
the inversion of Eliashberg equations and the determination of the
electron-phonon spectral function and the coulomb pseudopotential from
tunneling measurements in high-Tc superconductors. In order to compare the
calculated density of states ... | physics |
7,081 | The Current-Temperature Phase Diagram of Layered Superconductors | cond-mat.supr-con | The behavior of clean layered superconductors in the presence of a finite
electric current and in zero-magnetic field behavior is addressed. The
structure of the current temperature phase diagram and the properties of each
of the four regions will be explained. We will discuss the expected current
voltage and resistanc... | physics |
7,082 | A Constraint on the Anomalous Green's Function | cond-mat.supr-con | It is shown that the physical constraint of the Anomalous Green's function
gives a natural pairing condition. The resulting self-consistency equation is
directly related to the BCS gap equation. Both inhomogeneous and homogeneous
systems are considered to illustrate the importance of the constraint.
Especially we find ... | physics |
7,083 | Linear response and collective oscillations in superconductors with d-wave pairing | cond-mat.supr-con | Simple and physically transparent equations for the linear response of
layered superconductors with d-wave symmetry of the order parameter are derived
by means of the quasiclassic kinetic theory of superconductivity. Responses to
solenoidal and potential electric fields have different frequency dependencies.
The conduc... | physics |
7,084 | The c axis optical conductivity of layered systems in the superconducting state | cond-mat.supr-con | In this paper, we discuss the c axis optical conductivity Re [sigma_c(omega)]
in the high T_c superconductors, in the superconducting state. The basic
premise of this work is that electrons travelling along the c axis between
adjacent CuO_2 layers must pass through several intervening layers. In earlier
work we found t... | physics |
7,085 | The role of intermediate layers in the c-axis conductivity of layered superconductors | cond-mat.supr-con | A simplified model of c axis transport in the high T_c superconductors is
presented. Expressions are found for the c axis optical conductivity, the d.c.
resistivity, and the c axis penetration depth. Within the framework of this
model, the pseudogap in the optical conductivity arises naturally as a result
of the layere... | physics |
7,086 | Superfluid characteristics of the attractive Hubbard model for various lattice structures | cond-mat.supr-con | We study the basic thermodynamic and electromagnetic properties of the
superconductor described by the negative-$U$ Hubbard model (gap parameter
$\Delta$, critical temperature $T_c$, London penetration depth $\lambda$,
thermodynamic critical field $H_c$ and Ginzburg-Landau correlation length
$\xi_{G-L}$).The calculatio... | physics |
7,087 | Coupling between phonons and intrinsic Josephson oscillations in cuprate superconductors | cond-mat.supr-con | The recently reported subgap structures observed in the current-voltage
characteristic of intrinsic Josephson junctions in the high-T_c superconductors
Tl_2Ba_2Ca_2Cu_3O_{10+\delta} and Bi_2Sr_2CaCu_2O_{8+\delta} are explained by
the coupling between c-axis phonons and Josephson oscillations. A model is
developed where... | physics |
7,088 | Weak gravitation shielding properties of composite bulk YBa_2Cu_3O_{7-x} superconductor below 70 K under e.m. field | cond-mat.supr-con | A high-temperature YBa_2Cu_3O_{7-x} bulk ceramic superconductor with
composite structure has revealed weak shielding properties against
gravitational force while in a levitating state at temperatures below 70 K. A
toroidal disk was prepared using conventional ceramic technology in combination
with melt-texture growth. ... | physics |
7,089 | Effect of magnetic and non-magnetic impurities on highly anisotropic superconductivity | cond-mat.supr-con | We generalize Abrikosov-Gor'kov solution of the problem of weakly coupled
superconductor with impurities on the case of a multiband superconductor with
arbitrary interband order parameter anisotropy, including interband sign
reversal of the order parameter. The solution is given in terms of the
effective (renormalized)... | physics |
7,090 | Vortices and Quantum tunneling in Current-Biased 0-π-0 Josephson Junctions of d-wave Superconductors | cond-mat.supr-con | We study a current-biased 0-\pi-0 Josephson junction made by high-T_c
superconductors, theoretically. When a length of the \pi junction is large
enough, this junction contains a vortex-antivortex pair at both ends of the \pi
junction. Magnetic flux carried by the vortices is calculated using the
sine-Gordon equation. T... | physics |
7,091 | Disorder in two dimensional Josephson junctions | cond-mat.supr-con | An effective free energy of a two dimensional (i.e. large area) Josephson
Junctions is derived, allowing for thermal fluctuations, for random magnetic
fields and for external currents. We show by using replica symmetry breaking
methods, that the junction has four distinct phases: disordered, Josephson
ordered, a glass ... | physics |
7,092 | Extended Impurity Potential in a d_{x^2-y^2} Superconductor | cond-mat.supr-con | We investigate the role of a finite potential range of a nonmagnetic impurity
for the local density of states in a d_{x^2-y^2} superconductor. Impurity
induced subgap resonances are modified by the appearance of further scattering
channels beyond the $s$--wave scattering limit. The structure of the local
density of sta... | physics |
7,093 | Comment on "Superconducting gap anisotropy vs. doping level in high-T_c cuprates" by C. Kendziora et al, PRL 77, 727 (1996) | cond-mat.supr-con | In a recent paper Kendziora et al concluded that the superconducting gap in
overdoped Bi-2212 is isotropic. From data obtained from electronic Raman
scattering measurements, their conclusion was based on the observation that
pair breaking peaks occured at approximately the same frequency in different
scattering geometr... | physics |
7,094 | Local structure studies of the underdoped-overdoped transition in YBa_2Cu_3O_x. Measurement of the yttrium y-ray absorption fine structure | cond-mat.supr-con | We have measured the extended x-ray absorption-fine-structure (EXAFS) at the
Y-K edge of YBa_2Cu_3O_x for x=6.801, 6.947, 6.968, 6.984 at T=20-300 K. Across
the underdoped-overdoped transition the Y-Cu2 pairs exhibit harmonic vibrations
which freeze out in the superconducting phase, whereas the Y-O2,3 pairs exhibit
str... | physics |
7,095 | Subgap structures in the current-voltage characteristic of the intrinsic Josephson effect due to phonons | cond-mat.supr-con | A modified RSJ-model for the coupling of intrinsic Josephson oscillations and
c-axis phonons in the high-T_c superconductors Tl_2Ba_2Ca_2Cu_3O_{10+\delta}
and Bi_2Sr_2CaCu_2O_{8+\delta} is deveoped. This provides a very good
explanation for recently reported subgap structures in the I-V-characteristic
of the c-axis tra... | physics |
7,096 | Vortex-line liquid phases: Longitudinal superconductivity in the lattice London model | cond-mat.supr-con | We study the vortex-line lattice and liquid phases of a clean type-II
superconductor by means of Monte Carlo simulations of the lattice London model.
Motivated by a recent controversy regarding the presence, within this model, of
a vortex-liquid regime with longitudinal superconducting coherence over long
length scales... | physics |
7,097 | Stripes, Pseudogaps, and Van Hove Nesting in the Three-band tJ Model | cond-mat.supr-con | Slave boson calculations have been carried out in the three-band tJ model for
the high-T_c cuprates, with the inclusion of coupling to oxygen breathing mode
phonons. Phonon-induced Van Hove nesting leads to a phase separation between a
hole-doped domain and a (magnetic) domain near half filling, with long-range
Coulomb... | physics |
7,098 | Helicity Modulus and Fluctuating Type II Superconductors: Elastic Approximation and Numerical Simulations | cond-mat.supr-con | We develop the helicity modulus as a criterion for superconducting order in
the mixed phase of a fluctuating type II superconductor. We show that there is
a duality relation between this helicity modulus and the superfluid density of
a system of analog 2D bosons. We show that the vortex line lattice exhibits a
perfect ... | physics |
7,099 | Current-voltage relation for superconducting d-wave junctions | cond-mat.supr-con | We calculate the current-voltage (I-V) relation for planar superconducting
d-wave junctions for both arbitrary transmission of the junction and arbitrary
orientation of the d-wave superconductors. The midgap states (MGS) present at
interfaces/surfaces of a d-wave superconductor influence the I-V relation. In
some arran... | physics |
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