1,602 research outputs found
Interplane and intraplane heat transport in quasi two-dimensional nodal superconductors
We analyze the behavior of the thermal conductivity in quasi-two dimensional
superconductors with line nodes. Motivated by measurements of the anisotropy
between the interplane and intraplane thermal transport in CeIrIn_5 we show
that a simple model of the open Fermi surface with vertical line nodes is
insufficient to describe the data. We propose two possible extensions of the
model taking into account a) additional modulation of the gap along the axial
direction of the open Fermi surface; and b) dependence of the interplane
tunneling on the direction of the in-plane momentum. We discuss the temperature
dependence of the thermal conductivity anisotropy and its low T limit in these
two models and compare the results with a model with a horizontal line of nodes
(``hybrid gap''). We discuss possible relevance of each model for the symmetry
of the order parameter in CeIrIn_5, and suggest further experiments aimed at
clarifying the shape of the superconducting gap.Comment: 14pages, 12 figure
Dynamical Supersymmetry Breaking without Messenger Gauge Interactions
We investigate low-energy models of supersymmetry (SUSY) breaking by means of
vector-like gauge theories for dynamical SUSY breaking. It is not necessary to
introduce messenger gauge interactions utilized so far to mediate the SUSY
breaking to the standard-model sector, which reduces complication in the model
building. We also consider various other ways of SUSY-breaking transmission.Comment: 10 pages, LaTeX, 1 Postscript figur
Thermal conductivity in B- and C- phase of UPt_3
Although the superconductivity in UPt_3 is one of the most well studied,
there are still lingering questions about the nodal directions in the B and C
phase in the presence of a magnetic field. Limiting ourselves to the low
temperature regime (T<<Delta(0)), we study the magnetothermal conductivity with
in semiclassical approximation using Volovik's approach. The angular dependence
of the magnetothermal conductivity for an arbitrary field direction should
clarify the nodal structure in UPt_3.Comment: 4 pages, 5 figure
Anisotropy of in-plane magnetization due to nodal gap structure in the vortex state
We examine the interplay between anisotropy of the in-plane magnetization and
the nodal gap structure on the basis of the approximate analytic solution in
the quasiclassical formalism. We show that a four-fold oscillation appears in
the magnetization, and its amplitude changes sign at an intermediate field. The
high-field oscillation originates from the anisotropy of the upper critical
field, while the low-field behavior can be understood by the thermally
activated quasiparticles near nodes depending on the applied field angles. The
temperature dependence of the magnetization also shows a similar sign change.
The anisotropy of the magnetization offers a possible measurement to identify
the gap structure directly for a wide class of type II superconductors.Comment: 4 pages, 4 figure
Thermal conductivity through the quantum critical point in YbRh2Si2 at very low temperature
The thermal conductivity of YbRh2Si2 has been measured down to very low
temperatures under field in the basal plane. An additional channel for heat
transport appears below 30 mK, both in the antiferromagnetic and paramagnetic
states, respectively below and above the critical field suppressing the
magnetic order. This excludes antiferromagnetic magnons as the origin of this
additional contribution to thermal conductivity. Moreover, this low temperature
contribution prevails a definite conclusion on the validity or violation of the
Wiedemann-Franz law at the field-induced quantum critical point. At high
temperature in the paramagnetic state, the thermal conductivity is sensitive to
ferromagnetic fluctuations, previously observed by NMR or neutron scattering
and required for the occurrence of the sharp electronic spin resonance
fracture.Comment: 11 pages + Supplementary Material
Field-angle resolved specific heat and thermal conductivity in the vortex phase of UPd_2Al_3
The field-angle dependent specific heat and thermal conductivity in the
vortex phase of UPd_2Al_3 is studied using the Doppler shift approximation for
the low energy quasiparticle excitations. We first give a concise presentation
of the calculation procedure of magnetothermal properties with vortex and FS
averages performed numerically. The comparison of calculated field-angle
oscillations and the experimental results obtained previously leads to a strong
reduction of the possible SC candidate states in UPd_2Al_3. The possible SC gap
functions have node lines in hexagonal symmetry planes containing either the
zone center or the AF zone boundary along c. Node lines in non-symmetry planes
can be excluded. We also calculate the field and temperature dependence of
field-angular oscillation amplitudes. We show that the observed nonmonotonic
field dependence and sign reversal of the oscillation amplitude is due to small
deviations from unitary scattering.Comment: 16 pages, 8 figure
Thermoelectric response near a quantum critical point: the case of CeCoIn5
We present a study of thermoelectric coefficients in CeCoIn_5 down to 0.1 K
and up to 16 T in order to probe the thermoelectric signatures of quantum
criticality. In the vicinity of the field-induced quantum critical point, the
Nernst coefficient nu exhibits a dramatic enhancement without saturation down
to lowest measured temperature. The dimensionless ratio of Seebeck coefficient
to electronic specific heat shows a minimum at a temperature close to threshold
of the quasiparticle formation. Close to T_c(H), in the vortex-liquid state,
the Nernst coefficient behaves anomalously in puzzling contrast with other
superconductors and standard vortex dynamics.Comment: 4 pages, 4 figures,final published versio
Comparison of the Methods for the Background Reduction of Thick Targets in Routine PIXE Analysis
開始ページ、終了ページ: 冊子体のページ付
Quasiparticle spectrum of the hybrid s+g-wave superconductors YNi_2B_2C and LuNi_2B_2C
Recent experiments on single crystals of YNiBC have revealed the
presence of point nodes in the superconducting energy gap Delta(k} at k =
(1,0,0), (0,1,0), (-1,0,0), and (0,-1,0). In this paper we investigate the
effects of impurity scattering on the quasiparticle spectrum in the vortex
state of s+g-wave superconductors, which is found to be strongly modified in
the presence of disorder. In particular, a gap in the quasiparticle energy
spectrum is found to open even for infinitesimal impurity scattering, giving
rise to exponentially activated thermodynamic response functions, such as the
specific heat, the spin susceptibility, the superfluid density, and the nuclear
spin lattice relaxation. Predictions derived from this study can be verified by
measurements of the angular dependent magnetospecific heat and the
magnetothermal conductivity.Comment: 8 pages, RevTex, 4 figure
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