Evidence of a ferromagnetic Weyl semimetal in Mn(Bi,Sb)₄Te₇

Abstract:

Intrinsic antiferromagnetic topological insulators MnBi_2nTe_3n+1 (n=1, 2, 3) is one of the model material systems to explore exotic topological quantum states such as layer-independent quantum anomalous Hall insulator and axion insulator [1, 2]. Recently, Mn(Bi,Sb)₄Te₇ (MBST) is predicted to host a Weyl semimetal state in its ferromagnetic(FM) phase [3, 4]. In this talk, we will report the successful growth of the FM MBST system. Furthermore, we will also show both the carrier type and carrier concentration of this system can be controlled by tuning the Sb concentration. Our magnetotransport measurements reveal a transport signature of the predicted Weyl state in the lightly hole doped samples – chiral anomaly, as manifested by large negative longitudinal magnetoresistance. In contrast, the chiral anomaly effect is not observed in electron-doped or heavily hole doped samples, indicating the Weyl nodes are accessible only when the chemical potential is close to the valence band top.   

This work was supported by the US Department of Energy under grants DE-SC0019068.

References:

1. Liu et al., Nature Mater. 19, 522-527 (2020)

2. Deng et al., Science 367.6480:895-900 (2020)

3. Hu et al., PRB, 104, 054422 (2021)

4. Vidal et al., PRX, 9, 041065 (2019)