Unified approach to electrical and thermal transport in high-$T_c$ superconductors

TL;DR

This paper develops a unified theoretical framework for understanding electrical and thermal transport in high-$T_c$ superconductors, accounting for both fermionic and bosonic quasiparticles and their distinct temperature-dependent behaviors.

Contribution

It introduces a consolidated equation for low-field transport coefficients that incorporates two types of charge carriers and their characteristic temperatures, addressing complex transport phenomena in cuprates.

Findings

Explains pseudogap signatures in resistivity at $T^*$.

Provides fits to temperature-dependent resistivity data.

Implications for thermoelectric properties are discussed.

Abstract

In this paper we present a consolidated equation for all low-field transport coefficients, based on a reservoir approach developed for non-interacting quasiparticles. This formalism allows us to treat the two distinct types of charged (fermionic and bosonic) quasiparticles that can be simultaneously present, as for example in superconductors. Indeed, in the underdoped cuprate superconductors these two types of carriers result in two onset temperatures with distinct features in transport: $T^*$, where the fermions first experience an excitation (pseudo)gap, and $T_c$, where bosonic conduction processes are dominant and often divergent. This provides the central goal of this paper, which is to address the challenges in thermoelectric transport that stem from having two characteristic temperatures as well as two types of charge carriers whose contributions can in some instances enhance each other and in others compete. We show how essential features of the cuprates (their bad-metal character and the presence of Fermi arcs) provide an explanation for the classic pseudogap onset signatures at $T^*$ in the longitudinal resistivity, $\rho_{xx}$. Based on the fits to the temperature-dependent $\rho_{xx}$, we present the implications for all of the other thermoelectric transport properties.