April 22 - 26, 2024
Seattle, Washington
May 7 - 9, 2024 (Virtual)
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2024 MRS Spring Meeting & Exhibit
QT01.02.07

Quantum Dynamics of Fermi Polarons in Doped Semiconductor Monolayers

When and Where

Apr 23, 2024
4:15pm - 4:45pm
Room 420, Level 4, Summit

Presenter(s)

Co-Author(s)

Xiaoqin Li1

The University of Texas at Austin1

Abstract

Xiaoqin Li1

The University of Texas at Austin1
In doped semiconductors, optically excited electron-hole pairs (i.e. excitons) can be treated as an impurity coupling to a Fermi sea. Atomically thin semiconductors provide a rich playground to explore the Fermi polaron problems where the electrons and excitons further acquire a valley index. The attractive interaction between the exciton and Fermi sea leads to an energetically favorable state --- the attractive polaron --- as well as a higher energy repulsive polaron, a metastable state that eventually decays into attractive polarons. Here, we study the emergence and evolution of attractive polarons and repulsive polarons in MoSe<sub>2</sub> and WSe<sub>2</sub> monolayers as the electron doping density increases. Using two-dimensional coherent electronic spectroscopy (2DCES), we follow the changes in resonant energy, oscillator strength, and quantum decoherence of the AP and RP branches. Because of their different band structures, polarons in MoSe<sub>2</sub> and WSe<sub>2</sub> monolayers exhibit distinct quantum quantum dynamics and coupling mediated by valley index. Because of the large oscillator strength associated with quasi-particles, their intrinsic dephasing dynamics occur on sub-picosecond time scales. On the other hand, long-lived population and valley dynamics have been reported in previous experiments. We attribute such dynamics from a few hundred picoseconds to a few nanoseconds to dark-to-bright exciton conversion processes.<br/><br/><br/>We gratefully acknowledge funding the Department of Energy, Office of Basic Energy Sciences under grant DE-SC0019398 and the Welch Foundation grant F-1662 for sample preparation. Collaborations are enabled by National Science Foundation via MRSEC grants DMR-1720595 and DMR-2308817.

Keywords

optical properties

Symposium Organizers

Ajay Ram Srimath Kandada, Wake Forest University
Nicolò Maccaferri, Umeå University
Chiara Trovatello, Columbia University
Ursula Wurstbauer, Technical University of Munich

Symposium Support

Bronze
LIGHT CONVERSION

Session Chairs

Veronica Policht
Ursula Wurstbauer

In this Session