报告题目： Excitons are
Super!
报 告 人：薛飞（University
of Texas at Austin）
报告时间：2017年11月23日（星期四），下午2:30
报告地点：威廉希尔六层学术报告厅（致知楼3623）
报告摘要：
Long-range Coulomb interaction plays a significant role in
low dimensional systems. In this talk, we will present a few examples how
Coulomb interaction can modify, even induce new phases of matter. First example
is spatially indirect exciton condensates(SIEXC) in the case of a
two-dimensional semiconductor bilayer formed by two transition metal
dichalcogenides (TMD) that are separated and surrounded by an insulator, for
example hexagonal boron nitride (hBN). Because of the spin and valley degrees
of freedom, there are two distinct condensate phases with different number of
condensate flavors as layer separation and exciton density vary. Second example
is exciton-polariton condensate in multiple quantum wells system which can be
described by a microscopic equilibrium polariton condensate theory. We treat
exciton conduction and valence band states explicitly providing a mechanism for
electrical manipulation of polariton condensates. Third example is new interaction-induced
time-reversal symmetry broken nematic insulator(NTRB) phase near normal
insulator/ quantum spin Hall insulator phase transitions. We demonstrate that
this NTRB is inevitable because of the large energy difference between s-wave
and p-wave excitons. Last example is Weyl semimetal instability against
long-range Coulomb interaction. Though strong enough interaction can open the
gap by internode interband pairing, finite band Chern number jumps are retained
indicating the robustness of the topological non-trivial features.
报告人简介：
Fei Xue is a Ph. D candidate in physics department in
University of Texas at Austin. He earns his B.S. from Nanjing University in 2012, working in
Dr. Chunfeng Zhang and Dr. Min Xiao’s group on ultrafast optics. He is
currently working with Dr. Allan MacDonald on condensed matter theory and
interested in various many-electron problems.
欢迎广大师生参加！
威廉希尔
2017年11月16日
