»ã±¨±êÌâ (Title)£ºPossible Unconventional Exciton Superfluids in Two-dimensional Semiconductors£¨¶þά°ëµ¼ÌåÖпÉÄÜ´æÔڵļ«¶È¹æ¼¤×Ó³¬Á÷Ì壩

»ã±¨ÈË (Speaker)£ºÖìÆðÖÒ, (»ªÄÏʦ·¶´óѧ)

»ã±¨¹¦·ò (Time)£º2025Äê2ÔÂ21ÈÕ(ÖÜÎå) 14:00-17:00

»ã±¨µØÖ· (Place)£ºÐ£±¾²¿ G313

Ô¼ÇëÈË (Inviter)£ºÕÅÓÀƽ

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ÌáÒª: 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¨Cantivortex 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 ¡Ìq, 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.