Thermal transport across a continuous metal-insulator transition

TL;DR

This study investigates thermal transport behavior near a continuous metal-insulator transition in the Falicov-Kimball model, revealing robust quantum critical scaling and the survival of the Wiedemann-Franz law at zero temperature despite the absence of quasiparticles.

Contribution

It uncovers novel quantum critical scaling in thermal transport near the MIT and explains the mechanisms behind energy transport when charge transport is blocked.

Findings

Quantum critical scaling in thermal transport across the MIT.

Wiedemann-Franz law persists at T=0 even without quasiparticles.

Energy-current correlations are key to understanding thermal transport.

Abstract

The celebrated Wiedemann-Franz (WF) law is believed to be robust in metals as long as interactions between electrons preserve their fermion-quasiparticle character. We study thermal transport and the fate of the WF law close to a continuous metal-insulator transition (MIT) in the Falicov-Kimball model (FKM) using cluster-dynamical mean-field theory (CDMFT). Surprisingly, as for electrical transport, we find robust and novel quantum critical scaling in thermal transport across the MIT. We unearth the deeper reasons for these novel findings in terms of (i) the specific structure of energy-current correlations for the FKM and (ii) the microscopic electronic processes which facil- itate energy transport while simultaneously blocking charge transport close to the MIT. However, within (C)DMFT, we also find that the WF law survives at T=0 in the incoherent metal right up to the MIT, even in absence of Landau quasiparticles.