Flipping exciton angular momentum with chiral phonons in MoSe<sub>2</sub>/WSe<sub>2</sub> heterobilayers
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, C Faugeras
Abstract
Abstract 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—J Z = L Z +S Z – associated with the C 3 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∓</mml:mo> <mml:mn>2</mml:mn> </mml:math> thanks to the C 3 symmetry. These experiments reveal the crucial role of electron-phonon interaction in the carrier dynamics of group 6 transition metal dichalcogenides.