*

Spin-valley locking in the band structure of in monolayers of group-VI transition metal dichalcogenides such as MoS₂ has attracted enormous interests. In this talk, we report a non-centrosymmetric Dirac semimetal BaMnSb₂ is characterized by spin-valley locking^[1]. This is revealed by comprehensive studies using first-principle calculations, tight-binding and effective model analyses, and angle-resolved photoemission spectroscopy. Moreover, this material also exhibits a stacked quantum Hall effect. The spin-valley degeneracy extracted from the plateau height of quantized Hall resistivity is close to 2, further confirming the spin-valley locking picture. In the extreme quantum limit, we have also observed a two-dimensional chiral metal at the side surface. 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.
[1] Liu et al., arXiv:1907.06318