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卫健学术沙龙:基于5G+人工智能的心理/精神健康服务与管理体系建设
Gauging spacetime inversions
AI合成化学前沿与战略研讨会暨国家智能化学数据中心启动会
Macro to micro- and nano-scale fluidic engineering for analytical chemistry
报告题目:
IASTU Physics Seminars (biweekly):Nematic quantum paramagnet in spin-1 square lattice models: possible application to FeSe
 报告人:
Fa Wang
Peking University
报告时间:
2015-03-25 16:00
报告地点:
Conference Hall 322, Science Building, Tsinghua University
主办单位:
高等研究院
  简介:

(3:30~4:00pm, Tea, Coffee, and Cookie)

For spin-1/2 systems when quantum fluctuations destroy the Neel long-range order and open a
spin gap, the resulting state usually breaks the lattice translation and rotation symmetries. This
can be understood as reflecting aBerry's phase associatedwith the magnetic monopole of the
Neel order parameter. Here we point out the same Berry phase causes spin-1 systems to
spontaneously break the discrete rotational symmetry of the crystal while preserving its
translation symmetry. We support this claim by presenting an exactly solvable microscopic
model whose ground state is a nematic quantum paramagnet. In addition we derive a field
theory to describe the continuous, Landau-forbidden phase transition between a Neel ordered
state and a nematic quantum paramagnet, and compare the theory with existing numerical
results. We propose that the nematic quantum paramagnetic state captures essential features of
bulk FeSe which becomes nematic around 90K but does not develop any spin long range
order down to the lowest measured temperature.

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