Seminars Archive

Observation of Valley-Selective Linear Dichroism in Bilayer MoS₂

Abstract
It is by now well understood that circular dichroism arises in single-layer trigonal prismatic MoS₂ due to the lack of inversion symmetry in the single layer and to the resultant spin polarization of the valence band at the K and K’ points of the Brillouin zone. In the simplest picture, then, one might expect to see no dichroism at all in bilayer MoS₂, where inversion symmetry is restored. Nevertheless, our recent results obtained by pump-probe angle-resolved photoemission spectroscopy at the U.K. Artemis material science beamline reveal a strong and previously unpredicted linear dichroism at K and K’. In this talk, I will discuss these results and explain how they arise intrinsically, in connection with the trigonal warping of the valence band in the K and K’ valleys. I will also present a brief update on the status of the Artemis user facility’s upgrades to a new 100-kHz laser source.