2,333 research outputs found
Searching for zeroes: unconventional superconductors in a magnetic field
We review the results of the microscopic approach to the calculation of the
anisotropy in the specific heat in unconventional superconductors under rotated
field. Treating vortex scattering on equal footing with the energy shift we
find that the electronic specific heat may have minima or maxima when the field
is aligned with the nodes, depending on the temperature and field range. We
discuss the influence of the paramagnetic limiting and Fermi surface shape on
the location of the inversion line.Comment: Proceedings of SCES-0
Unconventional superconductors under rotating magnetic field I: density of states and specific heat
We develop a fully microscopic theory for the calculations of the
angle-dependent properties of unconventional superconductors under a rotated
magnetic field. We employ the quasiclassical Eilenberger equations, and use a
variation of the Brandt-Pesch-Tewordt (BPT) method to obtain a closed form
solution for the Green's function. The equations are solved self-consistently
for quasi-two-dimensional () superconductors with the
field rotated in the basal plane. The solution is used to determine the density
of states and the specific heat. We find that applying the field along the gap
nodes may result in minima or maxima in the angle-dependent specific heat,
depending on the location in the T-H plane. This variation is attributed to the
scattering of the quasiparticles on vortices, which depends on both the field
and the quasiparticle energy, and is beyond the reach of the semiclassical
approximation. We investigate the anisotropy across the T-H phase diagram, and
compare our results with the experiments on heavy fermion CeCoIn.Comment: 18 pages, 10 figure
Nodes vs. minima in the energy gap of iron-pnictides from field-induced anisotropy
We develop the formalism for computing the oscillations of the specific heat
and thermal transport under rotated magnetic field in multiband superconductors
with anisotropic gap and apply it to iron-pnictides. We show that these
oscillations change sign at low temperatures and fields, which strongly
influences the conclusions about the gap structure based on experiment. We find
that recent measurements of the specific heat oscillations indicate that the
iron-based superconductors possess an anisotropic gap with deep minima or nodes
close to the line connecting electron and hole pockets. We make predictions for
the behavior of the thermal conductivity that will help distinguish between
these cases.Comment: 4+3 pages, published version with supplemen
Knight Shift in the FFLO State of a Two-Dimensional D-Wave Superconductor
We report on the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in
two-dimensional d-wave superconductors with magnetic field parallel to the
superconducting planes. This state occurs at high magnetic field near the
Pauli-Clogston limit and is a consequence of the competition between the pair
condensation and Zeeman energy. We use the quasiclassical theory to
self-consistently compute the spatially nonuniform order parameter. Our
self-consistent calculations show that the FFLO state of a d-wave order
parameter breaks translational symmetry along preferred directions. The
orientation of the nodes in real space is pinned by the nodes of the basis
function in momentum space. Here, we present results for the Knight shift and
discuss the implications for recent nuclear magnetic resonance measurements on
CeCoIn5.Comment: 2 pages, 3 figures: LT-24 Conference, Orlando, Aug. 2005; to appear
in AIP Conference Proceeding
Spectrum of third sound cavity modes on superfluid He films
We report theoretical calculations of the spectrum of third sound modes for a
cylindrically symmetric film of superfluid He, and compare these results
with experimental data for the mode frequencies and amplitude spectrum of
surface waves of superfluid He films.Comment: 8 pages, 5 figures, LaTeX, submitted to JLT
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