Anomalous Nernst Effect in Dirac Semimetal Cd3As2

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 $\ddot{I}{„}_{tr}$ 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.

13 pages, 7 figures