Magnetically tunable Shubnikov-de Hass oscillations in MnBi2Te4

TL;DR

This study reports the direct observation of magnetically tunable Shubnikov-de Hass oscillations in MnBi2Te4, revealing the evolution of its band structure and Weyl semimetal phase under varying magnetic fields and orientations.

Contribution

It provides the first direct measurement of quantum oscillations in MnBi2Te4 and demonstrates how magnetic fields can tune its topological and electronic properties.

Findings

Oscillation period decreases with magnetic field

Nontrivial Berry phase indicates Weyl semimetal phase

Splitting of oscillations with magnetization rotation

Abstract

Shubnikov-de Hass oscillations are directly observed in undoped antiferromagnetic topological insulator MnBi2Te4. With increasing magnetic fields, the oscillation period decreases gradually in the magnetic transition from canted antiferromagnetism to ferromagnetism and then saturates in high magnetic fields, indicating the field-induced evolution of the band structure. From the analysis of the high-field oscillations, a nontrivial Berry phase and a small effective mass are extracted, in agreement with the predicted Weyl semimetal phase in ferromagnetic MnBi2Te4. Furthermore, rotating the magnetization of MnBi2Te4 can lead to a splitting of the high-field oscillations, which suggests the enhanced asymmetry of the Weyl cones in tilted fields. Therefore, the observation of these magnetically tunable quantum oscillations clearly demonstrates the indispensable role of field in tuning the band structure or physical properties of MnBi2Te4.