Abstract
Spin-valley locking in the band structure of monolayers of MoS₂ and other group-VI transition metal dichalcogenides (TMDCs) has garnered significant interest due to its potential for valleytronic and optoelectronic applications. This exotic electronic state is rarely observed in bulk materials. In this talk, I will present the discovery of a bulk spin-valley locked electronic state in the 3D non-centrosymmetric Dirac material BaMnSb₂ [1]. This state has been uncovered through a combination of first-principles calculations, tight-binding and effective model analyses, and angle-resolved photoemission spectroscopy measurements. Moreover, BaMnSb₂ exhibits a stacked quantum Hall effect (QHE), with the spin-valley degeneracy, derived from the QHE, being close to 2. This, along with Landau level spin splitting, further corroborates the presence of spin-valley locking in BaMnSb₂. Recently, we also discovered that this spin-valley locked state induces an intrinsic nonlinear Hall effect at room temperature. This is characterized by a second-harmonic and rectified Hall voltage response, driven by alternating current, under time-reversal symmetry [2]. These findings extend the understanding of coupled spin and valley physics from 2D systems into 3D systems. In addition, I will report on a colossal nonreciprocal Hall effect, driven by an exceptionally strong extrinsic nonlinear Hall effect, which arises from geometrically asymmetric scattering of textured Pt nanoparticles [3].
References
[1] Liu et al., Nature Communications 12, 4062(2021).
[2] Min et al., Nature Communications 14, 364(2023).
[3] Min et al., Nature Materials, (2024) https://www.nature.com/articles/s41563-024-02015-7
Please contact phweb@ust.hk should you have questions about the talk.
