Long-lived nanosecond spin relaxation and spin coherence of electrons in monolayer MoS2 and WS2

By Luyi Yang, Nikolai Sinitsyn, Weibing Chen, Jiangtan Yuan, Jing Zhang, J. Lou, S. Crooker. Nature Physics, 2015

285 citations recorded by the source corpus.

A range of semiconductors can host both spin and valley polarizations. Optical experiments on single layers of transition metal dichalcogenides now show that inter-valley scattering can accelerate spin relaxation. The recently discovered monolayer transition metal dichalcogenides (TMDCs) provide a fertile playground to explore new coupled spin–valley physics1,2,3. Although robust spin and valley degrees of freedom are inferred from polarized photoluminescence (PL) experiments4,5,6,7,8, PL timescales are necessarily constrained by short-lived (3–100 ps) electron–hole recombination9,10. Direct probes of spin/valley polarization dynamics of resident carriers in electron (or hole)-doped TMDCs, which may persist long after recombination ceases, are at an early stage11,12,13. Here we directly measure the coupled spin–valley dynamics in electron-doped MoS2 and WS2 monolayers using optical Kerr spectroscopy, and reveal very long electron spin lifetimes, exceeding 3 ns at 5 K (two to three orders of magnitude longer than typical exciton recombination times). In contrast with conventional III–V or II–VI semiconductors, spin relaxation accelerates rapidly in small transverse magnetic fields. Supported by a model of coupled spin–valley dynamics, these results indicate a novel mechanism of itinerant electron spin dephasing in the rapidly fluctuating internal spin–orbit field in TMDCs, driven by fast inter-valley scattering. Additionally, a long-lived spin coherence is observed at lower energies, commensurate with localized states. These studies provide insight into the physics underpinning spin and valley dynamics of resident electrons in atomically thin TMDCs.

Subfields: Electrical and Electronic Engineering, Materials Chemistry, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/8ffa631619971b5af9a324aa4dd58df32cee0271

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Citations in the corpus

Excitonic linewidth approaching the homogeneous limit in MoS2-based van der Waals heterostructures (2017, background): “Also, all timeresolved experiments using pulsed laser, such as pumpprobe spectroscopy, time-resolved PL, and four-wave mixing [12,31,36,90,91], will benefit from these samples with much higher threshold for optical damage as compared to uncapped samples.”