arXiv subjects

P. J. Hirschfeld

Publications and source records attributed to P. J. Hirschfeld.

240 records · Page 14Linked to original sources

arXiv1995

Heat Transport and the Nature of the Order Parameter in Superconducting $UPt_3$

Recent thermal conductivity data on the heavy fermion superconductor $UPt_3$ have been interpreted as offering support for an $E_{2u}$ model of the order parameter as opposed to an $E_{1g}$ model. In this paper, we analyze this issue from a theoretical standpoint including the detailed effects of Fermi surface and gap anisotropy. Our conclusion is that although current data put strong constraints on the gap anisotropy, they cannot definitively distinguish between these two models. Measurements on samples of varying quality could be decisive in this regard, however.

cond-mat↗

arXiv1995

Transport Properties of "Extended-s" State Superconductors

Superconducting states with "extended s-wave" symmetry have been suggested in connection with recent ARPES experiments on BSCCO. In the presence of impurities, thermodynamic properties of such states reflect a residual density of states $N(0)$ for a range of concentrations. While properties reflecting $N(ω)$ alone will be similar to those of d-wave states, transport measurements may be shown to qualitatively distinguish between the two. In contrast to the d-wave case with unitarity limit scattering, limiting low-temperature residual conductivities in the s-wave state are large and scale inversely with impurity concentration.

cond-mat↗

arXiv1994

Thermal Conductivity Anisotropy in Superconducting $UPt_3$

Recent thermal conductivity measurements on $UPt_3$ single crystals by Lussier et al. indicate the existence of a strong b--c anisotropy in the superconducting state. We calculate the thermal conductivity in various unconventional candidate states appropriate for the $UPt_3$ ``B phase" and compare with experiment, specifically the $E_{2u}$ and $E_{1g}$ $(1,i)$ states predicted in some Ginzburg-Landau analyses of the phase diagram. For the simplest realizations of these states over spherical or ellipsoidal Fermi surfaces, the normalized $E_{2u}$ conductivity is found, surprisingly, to be completely isotropic. We discuss the effects of inelastic scattering and realistic Fermi surface anisotropy, and deduce constraints on the symmetry class of the $UPt_3$ ground state.

cond-mat↗

arXiv1994

Multichannel Kondo impurities in superconductors

We discuss the effect of multichannel Kondo impurities on superconductivity. In the strong coupling regime such impurities are pairbreakers, in contrast to the ordinary Kondo effect. Measurements of $T_c$-suppression may help in identifying impurities displaying this more exotic exchange coupling to the conduction band.

cond-mat↗

arXiv1994

d-Wave Model for Microwave Response of High-Tc Superconductors

We develop a simple theory of the electromagnetic response of a d- wave superconductor in the presence of potential scatterers of arbitrary s-wave scattering strength and inelastic scattering by antiferromagnetic spin fluctuations. In the clean London limit, the conductivity of such a system may be expressed in "Drude" form, in terms of a frequency-averaged relaxation time. We compare predictions of the theory with recent data on YBCO and BSSCO crystals and on YBCO films. While fits to penetration depth measurements are promising, the low temperature behavior of the measured microwave conductivity appears to be in disagreement with our results. We discuss implications for d-wave pairing scenarios in the cuprate superconductors.

cond-mat↗

arXiv1994

Low Temperature Properties of Anisotropic Superconductors with Kondo Impurities

We present a self-consistent theory of superconductors in the presence of Kondo impurities, using large-$N$ slave-boson methods to treat the impurity dynamics. The technique is tested on the s-wave case and shown to give good results compared to other methods for $T_K > T_c$. We calculate low temperature thermodynamic and transport properties for various superconducting states, including isotropic s-wave and representative anisotropic model states with line and point nodes on the Fermi surface.

cond-mat↗