Zeeman field-induced two-dimensional Weyl semimetal phase in cadmium arsenide

TL;DR

This paper demonstrates a topological phase transition in cadmium arsenide thin films induced by an in-plane Zeeman field, leading to a two-dimensional Weyl semimetal phase with distinctive transport properties and quantum Hall effects.

Contribution

It predicts and experimentally supports the emergence of a 2D Weyl semimetal phase in Cd3As2 under magnetic and electric field tuning, a novel topological state.

Findings

Observation of saturated resistivities near h/e^2 over magnetic field range

Detection of odd integer quantum Hall effect in the 2D WSM phase

Minimal four-band model explains the experimental results

Abstract

We report a topological phase transition in quantum-confined cadmium arsenide (Cd3As2) thin films under an in-plane Zeeman field when the Fermi level is tuned into the topological gap via an electric field. Symmetry considerations in this case predict the appearance of a two-dimensional Weyl semimetal (2D WSM), with a pair of Weyl nodes of opposite chirality at charge neutrality that are protected by space-time inversion (C2T) symmetry. We show that the 2D WSM phase displays unique transport signatures, including saturated resistivities on the order of h/e^2 that persist over a range of in-plane magnetic fields. Moreover, applying a small out-of-plane magnetic field, while keeping the in-plane field within the stability range of the 2D WSM phase, gives rise to a well-developed odd integer quantum Hall effect, characteristic of degenerate, massive Weyl fermions. A minimal four-band k.p model of Cd3As2, which incorporates first-principles effective g factors, qualitatively explains our findings.