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Flipping exciton angular momentum with chiral phonons in MoSe2/WSe2 heterobilayers

Published on August 14, 2020

Optical selection rules in monolayers of transition metal dichalcogenides and of their heterostructures are determined by the conservation of the z-component of the total angular momentum—JZ = LZ+SZ – associated with the C3 rotational lattice symmetry which assumes half integer values corresponding, modulo 3, to distinct states. Here we show, based on polarization resolved and low temperature magneto-optical spectroscopy experiments, that the conservation of the total angular momentum in these systems leads to a very efficient exciton-phonon interaction when the coupling is mediated through chiral phonons. We identify these phonons as the Γ point E” modes which despite carrying angular momentum ± 1 are able to induce an excitonic spin-flip of -+2 thanks to the C3 symmetry. These experiments reveal the crucial role of electron-phonon interaction in the carrier dynamics of group 6 transition metal dichalcogenides.


A. Delhomme, D. Vaclavkova, A. Slobodeniuk, M. Orlita, M. Potemski, D. M. Basko, K. Watanabe, T. Taniguchi, D. Mauro, C. Barreteau, E. Giannini, A. F. Morpurgo, N. Ubrig and C. Faugeras

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