报告题目 (Title)：Possible Unconventional Exciton Superfluids in Two-dimensional Semiconductors（二维半导体中可能存在的非常规激子超流体）
报告人 (Speaker)：朱起忠(华南师范大学)
报告时间 (Time)：2025年2月21日(周五) 14:00-17:00
报告地点 (Place)：校本部 G313
邀请人 (Inviter)：张永平
主办部门：理学院物理系
摘要 (Abstract)：
地点：校本部G313
摘要: In conventional two-dimensional (2D) bosonic systems, true Bose-Einstein condensation (BEC) is impossible, and the superfluid-to-normal phase transition is governed by the Berezinskii-Kosterlitz-Thouless (BKT) mechanism with vortex–antivortex pair unbinding. This talk introduces a 2D bosonic system that demonstrates physics beyond this conventional paradigm: intralayer excitons in monolayer transition metal dichalcogenides. Due to intrinsic valley-orbit coupling and valley Zeeman energy, the exciton dispersion becomes linear at low momentum, resulting in several novel effects. Specifically, true BEC with long-range order is achieved with a nonzero critical temperature, the Goldstone mode exhibits an unconventional dispersion proportional to √q, vortex energies gain an additional linear term beyond their usual logarithmic dependence, and the superfluid-to-normal transition deviates from the BKT type beyond a characteristic system size. The model presented in this talk offers an exciting opportunity to investigate 2D superfluidity beyond the traditional BKT paradigm, with implications for both 2D materials and cold atoms.
