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

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

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

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

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

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

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

Nonlinear response and scaling law in the vortex state of d-wave superconductors

We study the field dependence of the quasi-particle density of states, the thermodynamics and the transport properties in the vortex state of d-wave superconductors when a magnetic field is applied perpendicular to the conducting plane, specially for the low field and the low temperature compared to the upper critical field and transition temperature, respectively, $H/H_{c2} \ll 1$ and $T/T_c \ll 1$. Both the superfluid density and the spin susceptibility exhibit the characteristic $\sqrt{H}$-field dependence, while the nuclear spin lattice relaxation rate T$_1^{-1}$ and the thermal conductivity are linear in field $H$. With increasing temperature, these quantities exhibit the scaling behavior in $T/\sqrt{H}$. The present theory applies to 2D $f$-wave superconductor as well; a possible candidate of the superconductivity in Sr$_2$RuO$_4$.Comment: 11 pages, 4 figure

Spectral properties and geology of bright and dark material on dwarf planet Ceres

Variations and spatial distributions of bright and dark material on dwarf planet Ceres play a key role in understanding the processes that have led to its present surface composition. We define limits for bright and dark material in order to distinguish them consistently, based on the reflectance of the average surface using Dawn Framing Camera data. A systematic classification of four types of bright material is presented based on their spectral properties, composition, spatial distribution, and association with specific geomorphological features. We found obvious correlations of reflectance with spectral shape (slopes) and age; however, this is not unique throughout the bright spots. Although impact features show generally more extreme reflectance variations, several areas can only be understood in terms of inhomogeneous distribution of composition as inferred from Dawn Visible and Infrared Spectrometer data. Additional material with anomalous composition and spectral properties are rare. The identification of the composition and origin of the dark, particularly the darkest material, remains to be explored. The spectral properties and the morphology of the dark sites suggest an endogenic origin, but it is not clear whether they are more or less primitive surficial exposures or excavated subsurface but localized material. The reflectance, spectral properties, inferred composition, and geologic context collectively suggest that the bright and dark material tends to gradually change toward the average surface over time. This could be because of multiple processes, i.e., impact gardening/space weathering, and lateral mixing, including thermal and aqueous alteration, accompanied by changes in composition and physical properties such as grain size, surface temperature, and porosity (compaction).Comment: Meteoritics and Planetary Science; Dawn at Ceres special issu