Verification of the Wiedemann-Franz law in YbRh2Si2 at a quantum critical point

TL;DR

This study confirms the Wiedemann-Franz law holds at the quantum critical point in YbRh2Si2, providing crucial insights into the nature of quantum criticality in heavy-fermion systems.

Contribution

The paper provides experimental evidence that the Wiedemann-Franz law is satisfied at the QCP in YbRh2Si2, challenging theories predicting its violation.

Findings

Wiedemann-Franz law holds at the QCP within experimental error

Thermal conductivity measurements down to 0.04 K

Constraints on models of unconventional quantum criticality

Abstract

The thermal conductivity measurements have been performed on the heavy-fermion compound YbRh2Si2 down to 0.04 K and under magnetic fields through a quantum critical point (QCP) at Bc = 0.66 T || c-axis. In the limit as T -> 0, we find that the Wiedemann-Franz law is satisfied within experimental error at the QCP despite the destruction of the standard signature of Fermi liquid. Our results place strong constraints on models that attempt to describe the nature of unconventional quantum criticality of YbRh2Si2.