Transport in Unconventional Superconductors

[600105] Hirschfeld将进行理论研究，以帮助确定氧化铜和重费米子超导体的配对状态，并发展临界温度以下输运的实用理论。主要的重点将放在无序和磁场对低温性能的影响上。先前的理论已经很好地描述了用脏d波图像反映无序依赖态准粒子密度的实验结果。将计算d波阶参数的散射振幅，包括自洽非对角线散射，以试图解决这类最简单模型在描述输运性质方面的不足。这种对理论的修正不能被忽视，而且很可能引入新的物理性质。在所有阶段，将与各向异性s波状态进行比较，以寻找质的差异。在理论中的几个例子中，偏离通常的模型球面或椭球面费米面可能导致新的定性效应将被研究。例如，利用六方各向异性打破UPt3的E2u配对场景中输运系数的伪各向同性，以及在YBCO和BSCCO的d波模型中由于正交性而产生的非对角散射矩阵元素。最后，将计算非常规超导体在有限磁场中的输运性质，计算非常规涡旋晶格最显著的不寻常特征，例如整个涡旋上的非束缚准粒子激发的大密度。这将涉及对来自单个d波涡旋的电子散射截面的仔细分析。包括杂质散射在内的半微观输运理论将被阐述并应用于超导状态下的热导率、电导率和霍尔系数的测量。将对高温超导体和所谓的重费米子超导体中超导性的各个方面进行理论研究。特别是，将研究输运性质以及无序和磁场对超导态性质的影响。＊＊＊

9600105 Hirschfeld Theoretical research designed to aid in the identification of the pairing state of the copper oxide and heavy fermion superconductors and the development of a practical theory of transport below the critical temperature will be conducted. The primary focus will be on the effect of disorder and magnetic field on low-temperature properties. Previous theory has provided a good description of experimental results reflecting the disorder-dependent quasiparticle density of states in terms of a dirty d-wave picture. Calculations of the scattering amplitude for a d-wave order parameter will be performed, including self-consistent off diagonal scattering, in an attempt to address inadequacies of the simplest models of this kind in the description of transport properties. Such corrections to the theory may not be ignored and are likely to introduce qualitatively new physics. At all stages, comparisons will be made with anisotropic s-wave states to search for qualitative differences. Several instances in the theory where deviations from the usual model spherical or ellipsoidal Fermi surface can lead to qualitatively new effects will be investigated. Examples include the breaking of spurious isotropy of transport coefficients in the E2u pairing scenario for UPt3 by hexagonal anisotropy, and the creation of matrix elements for off-diagonal scattering due to orthorhombicity in the d wave model for YBCO and BSCCO. Finally, transport properties of unconventional superconductors in a finite magnetic field will be calculated, accounting for the most significant unusual features of the unconventional vortex lattice, such as the large density of unbound quasiparticle excitations over the entire vortex. This will involve a careful analysis of the scattering cross-section for electrons from a single d-wave vortex. A semimicroscopic transport theory including impurity scattering will then be formulated and applied to measurements of thermal and electric al conductivities and Hall coefficients in the superconducting state. %%% Theoretical research will be conducted on various aspects of superconductivity in the high temperature superconductors and the so-called heavy-fermion superconductors. In particular, studies will be made of transport properties and on the effects of disorder and magnetic fields on superconducting state properties. ***