Thermal Conductivity as a Probe of Quasi-Particles in the Cuprates

TL;DR

This paper investigates the thermal conductivity in underdoped YBa2Cu3O_x to understand quasiparticle behavior, revealing a field-dependent mean-free-path and Hall angle that follow specific temperature dependencies, shedding light on quasiparticle dynamics in cuprates.

Contribution

It introduces a simple model to fit thermal conductivity data, enabling extraction of quasiparticle mean-free-path and Hall angle, linking thermal and electrical Hall effects in cuprates.

Findings

Quasiparticle Hall angle follows a 1/T^2 dependence.

Thermal conductivity fits a [1+p(T)|B|]^(-1) model.

Field dependence reveals quasiparticle scattering behavior.

Abstract

In underdoped YBa_2Cu_3O_x (x=6.63), the low-T thermal conductivity Kappa_xx varies steeply with field B at small B, and saturates to a nearly field-independent value at high fields. The simple expression [1+p(T)|B|]^(-1) provides an excellent fit to Kappa_xx(B) over a wide range of fields. From the fit, we extract the zero-field mean-free-path, and the low temperature behavior of the QP current. The procedure also allows the QP Hall angle Theta_QP to be obtained. We find that Theta_QP falls on the 1/T^2 curve extrapolated from the electrical Hall angle above Tc. Moreover, it shares the same T dependence as the field scale p(T) extracted from Kappa_xx. We discuss implications of these results.