335 research outputs found
Site-selective NMR for odd-frequency Cooper pairs around vortex in chiral p-wave superconductors
In order to identify the pairing symmetry with chirality, we study
site-selective NMR in chiral p-wave superconductors. We calculate local nuclear
relaxation rate 1/T_1 in the vortex lattice state by Eilenberger theory,
including the applied magnetic field dependence. We find that 1/T_1 in the NMR
resonance line shape is different between two chiral states
p_{pm}(=p_x{pm}ip_y), depending on whether the chirality is parallel or
anti-parallel to the vorticity. Anomalous suppression of 1/T_1 occurs around
the vortex core in the chiral p_- wave due to the negative coherence term
coming from the odd-frequency s-wave Cooper pair induced around the vortex with
Majorana state.Comment: 6 pages, 4 figure
Lower Critical Field Hc1(T) and Pairing Symmetry Based on Eilenberger Theory
We quantitatively estimate different T-dependences of Hc1 between s wave and
d wave pairings by Eilenberger theory. The T-dependences of Hc1(T) show
quantitative deviation from those in London theory. We also study differences
of Hc1(T) between p+ and p- wave pairing in chiral p wave superconductors.
There, Hc1(T) is lower in p- wave pairing, and shows the same T-dependence as
in s wave pairing.Comment: 2 pages, 1 figur
NMR relaxation time around a vortex in stripe superconductors
Site-dependent NMR relaxation time is calculated in the vortex
state using the Bogoliubov-de Gennes theory, taking account of possible
"field-induced stripe'' states in which the magnetism arises locally around a
vortex core in d-wave superconductivity. The recently observed huge enhancement
below at a core site in TlBaCuO is
explained. The field-induced stripe picture explains consistently other
relevant STM and neutron experiments.Comment: 4 pages, 4 figure
The effect of nonmagnetic impurities on the local density of states in s-wave superconductors
We study the effect of nonmagnetic impurities on the local density of states
(LDOS) in s-wave superconductors. The quasiclassical equations of
superconductivity are solved selfconsistently to show how LDOS evolves with
impurity concentration. The spatially averaged zero-energy LDOS is a linear
function of magnetic induction in low fields, N(E=0)=cB/H_{c2}, for all
impurity concentration. The constant of proportionality "c" depends weakly on
the electron mean free path. We present numerical data for differential
conductance and spatial profile of zero-energy LDOS which can help in
estimating the mean free path through the LDOS measurement.Comment: 7 pages, 7 figures (high quality color figure available on request
Anisotropic Diamagnetic Response in Type-II Superconductors with Gap and Fermi-Surface Anisotropies
Effects of anisotropic gap structures on a diamagnetic response are
investigated in order to demonstrate that the field-angle-resolved
magnetization () measurement can be used as a spectroscopic method
to detect gap structures. Our microscopic calculation based on the
quasiclassical Eilenberger formalism reveals that in a
superconductor with four-fold gap displays a four-fold oscillation reflecting
the gap and Fermi surface anisotropies, and the sign of this oscillation
changes at a field between and . As a prototype of
unconventional superconductors, magnetization data for borocarbides are also
discussed.Comment: 5 pages, 4 figure
Topological Structure of a Vortex in Fulde-Ferrell-Larkin-Ovchinnikov State
We find theoretically that the vortex core in the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is quite different from the
ordinary core by a simple topological reason. The intersection point of a
vortex and nodal plane of the FFLO state empties the excess spins. This leads
to observable consequences in the spatial structure of the spontaneous
magnetization. We analyze this topological structure based on the low lying
excitation spectrum by solving microscopic Bogoliubov-de Gennes equation to
clarify its physical origin.Comment: 4 pages, 4 figure
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