229 research outputs found
Classical phase fluctuations in d-wave superconductors
We study the effects of low-energy nodal quasiparticles on the classical
phase fluctuations in a two-dimensional d-wave superconductor. The
singularities of the phase-only action at T\to 0 are removed in the presence of
disorder, which justifies using an extended classical XY-model to describe
phase fluctuations at low temperatures.Comment: 14 pages, brief review for Mod. Phys. Lett.
Coexistence of Ferromagnetism and Superconductivity in Noncentrosymmetric Materials with Cubic Symmetry
This is a model study for the emergence of superconductivity in
ferromagnetically ordered phases of cubic materials whose crystal structure
lacks inversion symmetry. A Ginzburg-Landau-type theory is used to find the
ferromagnetic state and to determine the coupling of magnetic order to
superconductivity. It is found that noncentrosymmetricity evokes a helical
magnetic phase. If the wavelength of the magnetic order is long enough, it
gives rise to modulations of the order parameter of superconductivity, both in
modulus and complex phase. At magnetic domain walls the nucleation of
superconductivity is found to be suppressed as compared to the interior of
ferromagnetic domains.Comment: 5 pages, 2 figure
Non-Fraunhofer patterns of the anharmonic Josephson current influenced by a strong interfacial pair breaking
In the junctions with a strong Josephson coupling and a pronounced
interfacial pair breaking, the magnetic interference patterns of the Josephson
current are shown to differ substantially from the standard Fraunhofer shape.
The Fraunhofer pattern occurs, when Josephson couplings are weak. The narrow
peak of the critical current, centered at the zero magnetic field, and the
suppressed hills at finite field values are the characteristic features of the
non-Fraunhofer magnetic field modulation of the critical current, obtained in
this paper.Comment: 5 pages, 4 figure
Determining the superconducting gap structure in Sr2RuO4 from sound attenuation studies below Tc
This work presents a quantitative theoretical study of the sound attenuation
in the unconventional multiband superconductor Sr2RuO4 below the
superconducting transition temperature Tc. Sound attenuation in this material
is shown to have the remarkable property of being able to identify different
nodal structures on different bands. The nodal structures on the \gamma band on
the one hand, and on the \alpha and \beta bands on the other, are both found to
be characterized by the existence of point nodes, but are significantly
different in their quantitative aspects.Comment: 7 pages, REVTe
Singular Modes of the Electromagnetic Field
We show that the mode corresponding to the point of essential spectrum of the
electromagnetic scattering operator is a vector-valued distribution
representing the square root of the three-dimensional Dirac's delta function.
An explicit expression for this singular mode in terms of the Weyl sequence is
provided and analyzed. An essential resonance thus leads to a perfect
localization (confinement) of the electromagnetic field, which in practice,
however, may result in complete absorption.Comment: 14 pages, no figure
Localized surface states in HTSC: Alternative mechanism of zero-bias conductance peaks
It is shown that the quasiparticle states localized in the vicinity of
surface imperfections of atomic size can be responsible for the zero-bias
tunneling conductance peaks in high-Tc superconductors. The contribution from
these states can be easily separated from other mechanisms using their
qualitatively different response on an external magnetic field.Comment: REVTeX, 4 pages, 2 figs; to be published in PR
Quantum fluctuations in Larkin-Ovchinnikov-Fulde-Ferrell superconductors
We study the superconducting order parameter fluctuations near the phase
transition into the Larkin-Ovchinnikov-Fulde-Ferrell state in the clean limit
at zero temperature. In contrast to the usual normal metal-to-uniform
superconductor phase transition, the fluctuation corrections are dominated by
the modes with the wave vectors away from the origin. We find that the
superconducting fluctuations lead to a divergent spin susceptibility and a
breakdown of the Fermi-liquid behavior at the quantum critical point.Comment: 10 pages, 4 figure
Effect of disorder on the NMR relaxation rate in two-band superconductors
We calculate the effect of nonmagnetic impurity scattering on the
spin-lattice relaxation rate in two-band superconductors with the s-wave
pairing symmetry. It is found that for the interaction parameters appropriate
for MgB2 the Hebel-Slichter peak is suppressed by disorder in the limit of
small interband impurity scattering rate. In the limit of strong impurity
scattering, when the gap functions in the two bands become nearly equal, the
single-band behavior is recovered with a well-defined coherence peak just below
the transition temperature.Comment: 6 pages, 4 figure
Anisotropy in the helicity modulus of a quantum 3D XY-model: application to YBCO
We present a variational study of the helicity moduli of an anisotropic
quantum three-dimensional (3D) XY-model of YBCO in superconducting state. It is
found that both the ab-plane and the c-axis helicity moduli, which are
proportional to the inverse square of the corresponding magnetic field
penetration depth, vary with temperature T as T to the fourth power in the zero
temperature limit. Moreover, the c-axis helicity modulus drops with temperature
much faster than the ab-plane helicity modulus because of the weaker Josephson
couplings along the c-axis compared to those along the ab-plane. These findings
are in disagreement with the experiments on high quality samples of YBCO.Comment: 9 pages, 1 figur
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