Spin-valley locking for in-gap quantum dots in a MoS2 transistor

TL;DR

This paper demonstrates well-defined spin states in a MoS2 transistor, revealing spin-valley locking and anisotropic g-factors, advancing the potential for spin-valley quantum bits in atomically-thin semiconductors.

Contribution

It reports the first clear observation of spin-valley locking and quantifies spin-orbit splitting in a MoS2 transistor with high spectral resolution.

Findings

Observation of well-defined spin states at 150 mK.

Confirmation of spin-valley locking through Zeeman anisotropy.

Quantification of spin-orbit splitting as approximately 100 μeV.

Abstract

Spins confined to atomically-thin semiconductors are being actively explored as quantum information carriers. In transition metal dichalcogenides (TMDCs), the hexagonal crystal lattice gives rise to an additional valley degree of freedom with spin-valley locking and potentially enhanced spin life- and coherence times. However, realizing well-separated single-particle levels, and achieving transparent electrical contact to address them has remained challenging. Here, we report well-defined spin states in a few-layer MoS$ _2$ transistor, characterized with a spectral resolution of $\sim{50~\mu}$eV at ${T_\textrm{el} = 150}$~mK. Ground state magnetospectroscopy confirms a finite Berry-curvature induced coupling of spin and valley, reflected in a pronounced Zeeman anisotropy, with a large out-of-plane $g$-factor of ${g_\perp \simeq 8}$. A finite in-plane $g$-factor (${g_\parallel \simeq 0.55-0.8}$) allows us to quantify spin-valley locking and estimate the spin-orbit splitting ${2\Delta_{\rm SO} \sim 100~\mu}$eV. The demonstration of spin-valley locking is an important milestone towards realizing spin-valley quantum bits.