Spin-valley locking and bulk quantum Hall effect in a noncentrosymmetric Dirac semimetal BaMnSb2

Jinyu Liu ,Y B Zhang,M Jaime,C X Liu,Y Wang,Fedor Balakirev ,Jiabin Yu ,Cui-Zu Chang ,Leixin Miao ,Wei Ning ,Hemian Yi ,Yanglin Zhu ,You Lai ,Nasim Alem ,Franziska Weickert ,Kun Yang,Nitin Samarth ,Jianwei Sun ,Venkatraman Gopalan ,Jinliang Ning ,Bryan C Chakoumakos ,Jin Hu ,Lujin Min ,Timothy Pillsbury ,Ross Mcdonald ,Yi-Fan Zhao ,Kleyser Agueda Lopez ,Huibo Cao ,Zhiqiang Mao

doi:10.1038/s41467-021-24369-1

Abstract

Spin-valley locking in monolayer transition metal dichalcogenides has attracted enormous interest, since it offers potential for valleytronic and optoelectronic applications. Such an exotic electronic state has sparsely been seen in bulk materials. Here, we report spin-valley locking in a Dirac semimetal BaMnSb2. This is revealed by comprehensive studies using first principles calculations, tight-binding and effective model analyses, angle-resolved photoemission spectroscopy measurements. Moreover, this material also exhibits a stacked quantum Hall effect (QHE). The spin-valley degeneracy extracted from the QHE is close to 2. This result, together with the Landau level spin splitting, further confirms the spin-valley locking picture. In the extreme quantum limit, we also observed a plateau in the z-axis resistance, suggestive of a two-dimensional chiral surface state present in the quantum Hall state. These findings establish BaMnSb2 as a rare platform for exploring coupled spin and valley physics in bulk single crystals and accessing 3D interacting topological states.

Highlights

Spin-valley locking in monolayer transition metal dichalcogenides has attracted enormous interest, since it offers potential for valleytronic and optoelectronic applications
The above discussions have shown the Dirac cone at Kþ carries only upward spins, while the other one at KÀ has downward spins. This shares some similarity with the spin-valley locking of the monolayers group-VI TMDCs1–6, the spin-valley locking in BaMnSb2 exhibits several distinct features
The smaller band gap of Dirac cones compared to the spinorbital coupling (SOC) strength in our system implies that the Berry curvature for spin-up state is more concentrated around the Kþ (KÀ) valley, which can possibly lead to a more strongly coupled valley-spin Hall effect, as compared to transition metal dichalcogenides (TMDCs) monolayers and bulk 3R-MoS211

Summary

Introduction

Spin-valley locking in monolayer transition metal dichalcogenides has attracted enormous interest, since it offers potential for valleytronic and optoelectronic applications. The combination of inversion symmetry breaking and spinorbital coupling (SOC) in solid materials provides a route to achieve electronic states with spin polarization in the absence of magnetism When this occurs in a material possessing valleys in its conduction and valence bands, spin polarization becomes valley-dependent, creating a unique electronic state characterized by spin-valley locking. The spin-valley locked electronic band structure of group-VI TMDC monolayers gives rise to topological valley transport properties such as photo-induced charge Hall effect, valley Hall effect, and spin Hall effect under zero magnetic field[1,8,9], as well as valley-dependent optical selection rule[1,2,3,4] These exotic properties hold a great promise for potential applications in valleytronics, spintronics, and optoelectronics[10]. We have observed a plateau in the z-axis resistance in the quantum limit, which implies a 2D chiral surface metal present in the quantum Hall state

Methods

Results

Conclusion