Disorder recovers the Wiedemann-Franz law in the metallic phase of VO2

Abstract

At temperatures higher than 341 K, vanadium dioxide (${\mathrm{VO}}_{2}$) is a strongly correlated metal with resistivity exceeding the Mott-Ioffe-Regel limit. Its electronic thermal conductivity is lower than that predicted by the Wiedemann-Franz (WF) law, and can be explained by nonquasiparticle transport where heat and charge currents follow separate diffusive modes. In contradiction, the Wiedemann-Franz law is a direct consequence of quasiparticle transport where charge carriers are elastically scattered. In this work, we enhance elastic electron scattering in ${\mathrm{VO}}_{2}$ by introducing atomic disorder with ion irradiation. A gradual and eventually full recovery of the WF law is observed at high defect densities. This observation provides an example that connects hydrodynamic quasiparticle transport to nonquasiparticle transport in metallic systems.