Tunable Weyl Fermions in Chiral Tellurene in High Magnetic Fields

Published October 06, 2020

Left: “Hedgehog-like” Spin Structure Resulting from Chirality, Center: The Chiral Structure of Tellurene, Right: Quantum Hall Effect in Tellurene, tuned by a Gate Voltage

Topology, screws, spin and hedgehogs are words not normally found in the same scientific article but with the discovery of Weyl fermions in thin tellurine films they actually belong together. The work in this highlight describes how Qui et. al. used the unique properties of tellurine and high magnetic fields to identify the existence of Weyl fermions in a semiconductor. This discovery opens a new window into the intriguing world to topological materials.

What did scientists discover?

A new two-dimensional material, tellurene, was synthesized and a semiconducting device was fabricated from the thin film. Under strong magnetic fields, the quantum Hall effect was observed for the first time in tellurene. A finite Berry phase (equal to π) was measured from the quantum Hall oscillations measured in resistivity (bottom figure), suggesting the existence of Weyl fermions near the conduction band edge of tellurium, presumably associated with its chiral crystal structure (top figures).

Why is this important?

Weyl fermions have been sought in high-energy physics for nearly a century. Recent discoveries in condensed matter physics revealed that low-energy Weyl fermions can exist in topologically non-trivial materials. Our findings provide a new material to allow scientists to explore the physics of Weyl fermions in a controllable manner.

Who did the research?

Gang Qiu, Chang Niu, Yixiu Wang, Mengwei Si, Zhuocheng Zhang, Wenzhuo Wu, Peide D. Ye

Purdue University

Why did they need the MagLab?

The quantum Hall effect is an extraordinary behavior of electrons confined to a two-dimensional space that, in tellurene, can only be observed under strong magnetic fields and sub-Kelvin temperatures. By taking advantage of the 45 Tesla hybrid magnet - the strongest DC magnet in the world - the detailed energy spectrum of tellurene was resolved, unveiling its non-trivial topological properties directly from electrical resistivity.