Theory of field-modulated spin valley orbital pseudospin physics

Abstract

Pioneering studies in transition metal dichalcogenides have demonstrated convincingly the coexistence of multiple angular momentum degrees of freedom—of spin (1/2s_{z}=±1/2), valley (τ=K, K^{′} or ±1), and atomic orbital (l_{z}=±2) origins—in the valence band with strong interlocking among them, which results in noise-resilient pseudospin states ideal for spintronic-type applications. With field modulation a powerful, universal means in physics studies and applications, this work develops, from bare models in the context of complicated band structure, a general effective theory of field-modulated spin valley orbital pseudospin physics that is able to describe both intra- and intervalley dynamics. Based on the theory, it predicts and discusses the linear response of a pseudospin to external fields of arbitrary orientations. Paradigm field configurations are identified for pseudospin control, including pseudospin flipping. For a nontrivial example, it presents a spin valley orbital quantum computing proposal, where the theory is applied to address all-electrical, simultaneous control of s_{z}, τ, and l_{z} for qubit manipulation. It demonstrates the viability of such control with static field effects and an additional dynamic electric field. An optimized qubit manipulation time ∼O (ns) is given.