Quasiparticle transport and localization in high-T_c superconductors

TL;DR

This paper develops a theoretical framework for impurity effects in high-T_c superconductors, revealing a novel spin-metal phase and a quantum phase transition to a localized spin-insulator, with implications for transport properties.

Contribution

It introduces a non-linear sigma model approach to describe impurity scattering and quantum phase transitions in high-T_c superconductors.

Findings

Existence of a spin-metal phase with non-zero spin diffusion at zero temperature

Quantum phase transition to a spin-insulator with decreasing inter-layer coupling

Implications for spin and thermal transport measurements in experiments

Abstract

We present a theory of the effects of impurity scattering in d_{x^2-y^2} superconductors and their quantum disordered counterparts, based on a non-linear sigma model formulation. We show the existence, in a quasi-two-dimensional system, of a novel spin-metal phase with a non-zero spin diffusion constant at zero temperature. With decreasing inter-layer coupling, the system undergoes a quantum phase transition (in a new universality class) to a localized spin-insulator. Experimental implications for spin and thermal transport in the high-temperature superconductors are discussed.