Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides.

By Di Xiao, Gui-Bin Liu, W. Feng, Xiaodong Xu, W. Yao. Physical Review Letters, 2011

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We show that inversion symmetry breaking together with spin-orbit coupling leads to coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides, making possible controls of spin and valley in these 2D materials. The spin-valley coupling at the valence-band edges suppresses spin and valley relaxation, as flip of each index alone is forbidden by the valley-contrasting spin splitting. Valley Hall and spin Hall effects coexist in both electron-doped and hole-doped systems. Optical interband transitions have frequency-dependent polarization selection rules which allow selective photoexcitation of carriers with various combination of valley and spin indices. Photoinduced spin Hall and valley Hall effects can generate long lived spin and valley accumulations on sample boundaries. The physics discussed here provides a route towards the integration of valleytronics and spintronics in multivalley materials with strong spin-orbit coupling and inversion symmetry breaking.

Subfields: Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/87809db4bc0d63da6a0f30bea26b66513767ccae

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Citations in the corpus

Progress, challenges, and opportunities in two-dimensional materials beyond graphene. (2013, background): “Because inversion symmetry is broken in MoS2, the valley and spin degrees of freedom are coupled and new optical selection rules enable excitation of specific spin carriers into a specific valley, as illustrated in Figure 12c.(156,231) This spin-valley coupling forbids independent spin or valley fli”
Van der Waals engineering of ferromagnetic semiconductor heterostructures for spin and valleytronics (2017, background): “1D, dashed lines), including circularly polarized valley optical selection rules (29), spin-valley locking effects (30), and valley Zeeman splitting of about 0.”
Excitonic linewidth approaching the homogeneous limit in MoS2-based van der Waals heterostructures (2017, background): “(a) Chiral optical selection rules for interband optical transitions in nonequivalent valleys Kþ and K− [30,76].”
Stability and electronic structures of native defects in single-layer MoS 2 (2014, background): “Besides the large electronic correlation effects, the intrinsic broken inversion symmetry of the single-layer MoS2 induces the spin-orbit split bands at K and -K points in the hexagonal Brillouin zone [11] and opens the new era of the spin- and valley-controlled electronics [12–16].”
Valley-polarized exciton–polaritons in a monolayer semiconductor (2017, background): “edu degenerate excitons, identical in most properties, but with opposite Berry curvature and distinct response to light of opposite helicity depending on their valley pseudospin index [18] (Fig.”
Long-lived nanosecond spin relaxation and spin coherence of electrons in monolayer MoS2 and WS2 (2015, background): “This can arise, e.g., from manybody correlations while holes are present [2, 20], or preferential non-radiative recombination of holes with particular electron states (nonradiative processes account for the majority of recombination in TMDCs [5]).”