Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session F37: 2D Materials - Optics and Excitons III
11:15 AM–2:15 PM,
Tuesday, March 6, 2018
LACC Room: 411
Sponsoring Units: DMP DCOMP
Chair: Feng Wang, Univ of California - Berkeley
Abstract: F37.00003 : The Role of Dark Excitons in Valley Depolarisation In Monolayer Transition Metal Dichcalcogenides
11:39 AM–11:51 AM
We present a theoretical study of the valley magneto-exciton relaxation dynamics in monolayer transition metal dichcalcogenides (TMDs) using a kinetic equation approach. The TMDs are direct band gap semiconductors with strong light-matter coupling which produce optical responses dominated by tightly bound excitons. The combination of the lattice symmetry and strong spin-orbit interaction gives rise to a rich selection rules allowing for optical control of the excitons valley polarisation. Experiments have shown that due to spin-orbit interactions there are spin forbidden transitions which lead to dark exciton states, and these states are found to possess long lifetimes due to their non-radiative decay and play a role in the depolarisation dynamics of the TMDs. Using a kinetic equation approach we investigate the interplay of the exchange interaction, a perpendicular magnetic field and the dark state scattering the time evolution of the exciton valley polarisation. We find that the influence of the dark states leads to longer valley relaxation times. We also explore the effect of an in-plane magnetic, which acts to “brighten” the dark states, which leads to an even greater increase in the valley relaxation time.
The American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics.
1 Physics Ellipse, College Park, MD 20740-3844
Editorial Office 1 Research Road, Ridge, NY 11961-2701 (631) 591-4000
Office of Public Affairs 529 14th St NW, Suite 1050, Washington, D.C. 20045-2001 (202) 662-8700