Theory of field-modulated spin valley orbital pseudospin physics

Abstract

Pioneering studies in transition metal dichalcogenides have demonstrated convincingly the co-existence of multiple angular momentum degrees of freedom -of spin (1/2 sz = ±1/2), valley (τ = K, K' or ±1), and atomic orbital (lz = ±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 inter-valley 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 sz, τ, and lz 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.

Valley two-qubit system in a MoS$_2$-monolayer gated double quantum dot

“…It is known that for carriers that are spatially localized the valley degree of freedom is still well defined. There are many theoretical 17,[53][54][55][56][57][58][59][60][61][62][63][64] and experimental 51,[65][66][67][68][69] studies of quantum dots (QDs) based on MoS 2 and related TMDCs pointing towards promising routes to various spin-valley massive-Dirac-fermion-based qubit realizations, as summarized recently in Ref. [70].…”