Anomalous Nernst Effect in Dirac Semimetal Cd3As2

TL;DR

This paper reports the observation of a large anomalous Nernst effect in the Dirac semimetal Cd3As2, linked to Berry curvature and Weyl node formation, revealing novel transport phenomena at low temperatures.

Contribution

It provides experimental evidence of the anomalous Nernst effect in Cd3As2 and links it to Weyl node formation and Berry curvature effects.

Findings

Large anomalous Nernst signal observed in Cd3As2

Transport relaxation time increases below 50 K

Quantum oscillations show Dirac nodes splitting into Weyl states

Abstract

Dirac and Weyl semimetals display a host of novel properties. In Cd$_3$As$_2$, the Dirac nodes lead to a protection mechanism that strongly suppresses backscattering in zero magnetic field, resulting in ultrahigh mobility ($\sim$ 10$^7$ cm$^2$ V$^{-1}$ s$^{-1}$). In applied magnetic field, an anomalous Nernst effect is predicted to arise from the Berry curvature associated with the Weyl nodes. We report observation of a large anomalous Nernst effect in Cd$_3$As$_2$. Both the anomalous Nernst signal and transport relaxation time $\tau_{tr}$ begin to increase rapidly at $\sim$ 50 K. This suggests a close relation between the protection mechanism and the anomalous Nernst effect. In a field, the quantum oscillations of bulk states display a beating effect, suggesting that the Dirac nodes split into Weyl states, allowing the Berry curvature to be observed as an anomalous Nernst effect.