Unified approach to electrical and thermal transport in high-Tc superconductors

Abstract

In this paper, we present a consolidated equation for all low-field transport coefficients, based on a reservoir approach developed for noninteracting 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 Tc, 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, ρxx. Based on the fits to the temperature-dependent ρxx, we present the implications for all of the other thermoelectric transport properties.

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