Frontiers Seminar: Xiaoyang Zhu, Columbia University

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Date: March 29, 2021
Time: 3:30 p.m. - 4:30 p.m.
Location: Virtual event
Category: Seminar

Frontiers Seminar: Xiaoyang Zhu, Columbia University (Host: Rury)

Talk title: "Controlling Excitons in 2D"

Abstract:
An exciton is a quasi-particle consisting of an electron and a hole bound by the Coulomb potential. It is a solid and excited state analog of the hydrogen atom. Excitons are fundamental to semiconductors and determine a range of processes involving the conversion of light to charge or charge to light. As bosonic particles, many-body interaction of excitons can lead to quantum phases, e.g., Bose-Einstein condensates (BECs). Compared to their bulk counterparts, the exciton binding energy can be increased by order(s) of magnitude in low dimensional materials, such as zero-dimensional (0D) quantum dots (QDs) and two-dimensional (2D) quantum wells, a result of both spatial confinement and reduced dielectric screening of the electron-hole pair. In this lecture, I will discuss recent efforts in my laboratory on controlling excitons in 2D. We explore a number of approaches, including i) the spatial separation of the charge neutral exciton in a 2D transition-metal dichalcogenide (TMDC) monolayer into dipolar interlayer excitons in TMDC hetero-bilayers; ii) the spatial localization of 2D delocalized interlayer excitons into ordered arrays of 0D QD-like potential traps formed by the moiré pattern in TMDC heterobilayers; iii) the phase transitions of interlayer excitons: moiré trapped exciton lattice à free exciton gas à charge separated electron-hole plasmas, in TMDC heterobilayers; and iv) the switching on/off of interlayer electronic/excitonic hybridization by magnetic order in 2D magnetic semiconductor bilayers and multilayers. I will also briefly discuss our ongoing research on quantum phases of excitons.

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