Valley Zeeman effect in elementary optical excitations of monolayer WSe2
By A. Srivastava, Meinrad Sidler, A. Allain, D. Lembke, Andras Kis, A. Imamoğlu. Nature Physics, 2014
748 citations recorded by the source corpus.
Charge carriers in transition metal dichalcogenides have an extra degree of freedom known as valley pseudospin, which is associated with the shape of the energy bands. Experiments show that this pseudospin can be manipulated using magnetic fields. A monolayer of a transition metal dichalcogenide such as WSe2 is a two-dimensional direct-bandgap valley-semiconductor1,2 having an effective honeycomb lattice structure with broken inversion symmetry. The inequivalent valleys in the Brillouin zone could be selectively addressed using circularly polarized light fields3,4,5, suggesting the possibility for magneto-optical measurement and manipulation of the valley pseudospin degree of freedom 6,7,8. Here we report such experiments that demonstrate the valley Zeeman effect—strongly anisotropic lifting of the degeneracy of the valley pseudospin degree of freedom using an external magnetic field. The valley-splitting measured using the exciton transition deviates appreciably from values calculated using a three-band tight-binding model9 for an independent electron–hole pair at ±K valleys. We show, on the other hand, that a theoretical model taking into account the strongly bound nature of the exciton yields an excellent agreement with the experimentally observed splitting. In contrast to the exciton, the trion transition exhibits an unexpectedly large valley Zeeman effect that cannot be understood within the same framework, hinting at a different contribution to the trion magnetic moment. Our results raise the possibility of controlling the valley degree of freedom using magnetic fields in monolayer transition metal dichalcogenides or observing topological states of photons strongly coupled to elementary optical excitations in a microcavity10.
Subfields: Electrical and Electronic Engineering, Materials Chemistry
View Paper: https://www.semanticscholar.org/paper/46ed0d0c7fa1833f668d0b0e60adf4b48d276ff9
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Citations in the corpus
- Topological polaritons from quantum wells in photonic waveguides or microcavities (2014, neutral): “[40] Ajit Srivastava, Meinrad Sidler, Adrien V.”
- Excitons in atomically thin 2D semiconductors and their applications (2017, background): “[51] elucidated the influence of magnetic field on the spin, orbital, and valley angular momentums.”
- Giant and tunable valley degeneracy splitting in MoTe2 (2015, neutral): “[18] Ajit Srivastava, Meinrad Sidler, Adrien V.”
- Valley excitons in two-dimensional semiconductors (2015, background): “The second is the magnetic moment of atomic orbital or the intracellular component [33–36].”