Wiedemann-Franz law in a non-Fermi liquid and Majorana central charge: Thermoelectric transport in a two-channel Kondo system

TL;DR

This paper investigates the two-channel Kondo model's critical point, revealing that the Wiedemann-Franz law holds despite non-Fermi liquid behavior and demonstrating how heat conductivity can detect Majorana fractionalization.

Contribution

It provides an exact analysis showing the Wiedemann-Franz law's validity at the non-Fermi liquid critical point and proposes a method to measure the Majorana central charge via heat transport.

Findings

Wiedemann-Franz law holds at the critical point despite non-Fermi liquid physics.

Heat conductivity measurements can detect Majorana fractionalization.

The Majorana central charge c=1/2 can be experimentally accessed.

Abstract

Quantum dot devices allow one to access the critical point of the two-channel Kondo model. The effective critical theory involves a free Majorana fermion quasiparticle localized on the dot. As a consequence, this critical point shows both the phenomenon of non-Fermi liquid physics and fractionalization. Although a violation of the Wiedemann-Franz law is considered a defining feature of non-Fermi liquid systems, we show by exact calculations that it holds at the critical point, providing a counterexample to this lore. Furthermore, we show that the fractionalized Majorana character of the critical point can be unambiguously detected from the heat conductivity, opening the door to a direct experimental measurement of the elusive Majorana central charge $c=\tfrac{1}{2}$.