Magnetic field induced drastic violation of Wiedemann-Franz law in Dirac semimetal Cd$_{3}$As$_{2}$

TL;DR

This study reveals a significant violation of the Wiedemann-Franz law in the Dirac semimetal Cd$_{3}$As$_{2}$ under magnetic fields, indicating a breakdown of Landau Fermi-liquid theory and quasiparticle concept at high fields.

Contribution

It demonstrates the magnetic field-induced violation of Wiedemann-Franz law in Cd$_{3}$As$_{2}$, suggesting a quantum critical point and breakdown of quasiparticle description in this topological semimetal.

Findings

Wiedemann-Franz law is drastically violated under magnetic field.

Violation increases with magnetic field strength.

Indicates breakdown of Landau quasiparticles in Cd$_{3}$As$_{2}$.

Abstract

The journey through the nontrivial band topology beyond the conventional band structure has resulted in the recent discovery of three-dimensional Dirac semimetal phase in Na$_{3}$Bi and Cd$_{3}$As$_{2}$. The bulk state of which is semi-metallic obeying linear energy dispersion, while the surface state is topology protected Fermi arc. Due to the unique band topology, they show different exotic electronic properties of both fundamental and technological interest. From electrical and thermal transport measurements, we have demonstrated a remarkable violation of Wiedemann-Franz law (WFL) under application of magmatic field in Cd$_{3}$As$_{2}$ and the violation becomes more and more drastic with increasing magnetic field strength. Whereas the validity of WFL is the key feature of Landau Fermi-liquid theory in metal, the notion of quasiparticles is the building block to this theory. This implies that the fundamental concept of Landau quasiparticle no longer holds in Cd$_{3}$As$_{2}$ in presence of magnetic field. The continuous break down of Landau quasiparticle framework with field introduces a concept of field induced quantum critical point (QCP) as in the case of heavy fermion compounds YbRh$_{2}$Si$_{2}$, Sr$_{3}$Ru$_{2}$O$_{7}$, etc.