DRAFT

Special Chemical Physics Seminar

Tuesday, February 22, 2022
12:00pm to 1:00pm
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Online and In-Person Event
Ordering Excitons in Two Dimensions
Yusong Bai, Postdoctoral Scholar, Columbia University, Chemistry, Columbia,

Electrons or excitons (H-atom-like electron-hole pairs) can crystalize, analogous to the familiar crystallization of atoms and molecules in chemistry. The formation of electron or exciton crystals is predominantly determined by many-body quantum interactions, and they are thus commonly referred to as quantum phases of matter. Understanding and controlling such quantum phases is a central goal in research on quantum matter, and they are expected to play an essential role in the emerging quantum information sciences. At a fundamental level, the key factor which drives the ordering is the competition between the inter-particle potential energy and the particle's kinetic energy. In this regard, two-dimensional (2D) semiconductors that facilitate strong many-body Coulomb interactions due to reduced screening offer an excellent platform for the exploration of ordered states of electrons and excitons. In this talk, I will discuss my most recent research efforts to realize the ordered states of excitons. A number of approaches have been exploited, including (i) the formation of interlayer dipolar excitons with spatially separated electron and hole wavefunctions in 2D van der Waals heterobilayers of transition metal dichalcogenide (TMDC), (ii) the spatial localization of 2D delocalized interlayer excitons into arrays of zero-dimensional (0D) quantum-dot-like moiré potentials in the TMDC heterobilayer, and (iii) the crystallization of dipolar and quadrupolar excitons in double moiré TMDC trilayers. The goal is to understand how the fundamental factors, such as Coulomb interactions, kinetic energies, moiré potential traps, Fermionic exchange interactions, and quantum fluctuations, drive the formation of ordered exciton phases.

In-Person: Beckman Institute Auditorium

Online:

https://caltech.zoom.us/j/81915453662?pwd=aEUvSEtITTdIdkc0cERHNjVhNURzZz09

Meeting ID: 819 1545 3662

Passcode: yusongbai

Faculty Host: Lu Wei

For more information, please contact Cindy Kim by email at cjwkim@caltech.edu.