Flipping exciton angular momentum with chiral phonons in MoSe 2 /WSe 2 heterobilayers

A. Delhomme (1) , D Vaclavkova (1) , A. Slobodeniuk (1) , M. Orlita (1) , M. Potemski (1) , D. Basko (2) , K. Watanabe (3) , T. Taniguchi (3) , D Mauro (4) , C. Barreteau (4) , E. Giannini (4) , A Morpurgo (4) , N. Ubrig (4) , Clément Faugeras (1)

1 LNCMI-G - Laboratoire national des champs magnétiques intenses - Grenoble
2 LPM2C - Laboratoire de physique et modélisation des milieux condensés
3 NIMS - National Institute for Materials Science
4 DQMP - Department of Quantum Matter Physics [Geneva]

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.

Domaines: Physique [physics]; Matière Condensée [cond-mat]; Systèmes désordonnés et réseaux de neurones [cond-mat.dis-nn]; Science des matériaux [cond-mat.mtrl-sci]

A. Delhomme, D Vaclavkova, A. Slobodeniuk, M. Orlita, M. Potemski, et al.. Flipping exciton angular momentum with chiral phonons in MoSe 2 /WSe 2 heterobilayers. 2D Materials, 2020, 7 (4), pp.041002. ⟨10.1088/2053-1583/aba567⟩. ⟨hal-02926755⟩