SKM 2023 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 34: Ultrafast Electron Dynamics at Surface and Interfaces III
O 34.1: Vortrag
Dienstag, 28. März 2023, 10:30–10:45, TRE Phy
Resolving Intervalley Exciton Couplings in Atomically Thin Semiconductors with Multidimensional Spectroscopy — •Lawson Lloyd1,2, Ryan Wood2, Fauzia Mujid2, Siddhartha Sohoni2, Karen Ji2, Po-Chieh Ting2, Jacob Higgins2, Jiwoong Park2, and Gregory Engel2 — 1Fritz-Haber-Institut, Berlin, Germany — 2The University of Chicago, Chicago, IL, USA
Atomically thin transition metal dichalcogenides (TMDs) have emerged as promising candidates for next-generation optoelectronic applications. In particular, an optically addressable “valley” degree of freedom at the K/K’ points can be used to store and readout information by exploiting the valley-dependent chiral optical selection rules. However, intervalley coupling after optical excitation leads to a loss of the valley polarization on ultrafast timescales. Identifying the microscopic mechanisms driving valley depolarization is therefore critical to advancing useful applications.
Here, leveraging multidimensional electronic spectroscopy, we track the exciton dynamics and couplings in large-area monolayer MoS2 with femtosecond and valley resolution. We show that intervalley coupling between exciton states occurs both on the timescale of excitation (∼10 fs) and with minimal dependence on the excitation fluence, temperature, or sample grain size. These results shed light on the strong many-body interactions governing the femtosecond exciton dynamics in TMDs and the factors limiting the realization of novel technologies built around the valley degree of freedom.