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SUMMARY:Beyond Mean-Field Microscopic Theoretical Framework in Many-Body S
 ystems
DTSTART:20260922T060000Z
DTEND:20260922T070000Z
DTSTAMP:20260925T082000Z
UID:indico-event-5308@indico-tdli.sjtu.edu.cn
DESCRIPTION:Speakers: Fei Yang (杨飞) (HKUST)\n\nHost: Prof. Tao Dong 
  \nVenue: TDLI Meeting Room N600\nTencent Meeting link: https://meeting.
 tencent.com/dm/12EW8miKQBxq \nMeeting ID: 261744988\, no password\n \nAbs
 tract:\nUnderstanding how collective fluctuations reshape ordered states b
 eyond mean-field theory is a central challenge in modern many-body physics
 \, especially in low-dimensional and strongly interacting systems. In this
  talk\, we present a unified microscopic framework for phase transitions\,
  crossovers\, and decoherence phenomena driven by collective bosonic modes
  in superconductors\, Josephson systems\, and charge-density-wave material
 s.\nFor two-dimensional superconductors\, we develop a self-consistent the
 ory incorporating quasiparticles\, phase fluctuations\, disorder\, and BKT
  physics. We show how long-range Coulomb interactions modify phase modes\,
  overcoming the conventional Mermin–Wagner instability while retaining s
 trong fluctuation effects. The theory captures gate-tunable superconductiv
 ity in atomically thin systems and the disorder-driven evolution of superc
 onducting transitions and pseudogap regimes.\nWe further apply this framew
 ork to low-dimensional Josephson systems\, demonstrating that thermal phas
 e fluctuations can suppress interlayer coherence\, quench the Josephson di
 ode effect\, and drive phase-incoherent states even when the superconducti
 ng gap remains finite.\nFinally\, we develop a microscopic theory of latti
 ce-driven charge-density waves\, showing that thermally enhanced phason fl
 uctuations lead to phason softening\, hidden depinning crossovers\, amplit
 udon damping\, and ultimately first-order transitions.\nOverall\, these re
 sults establish a unified beyond-mean-field perspective on how collective 
 bosonic fluctuations govern ordering\, decoherence\, and hidden crossovers
  across a broad class of quantum materials.\n \nBiography:\nDr. Fei Yang 
 is a theoretical condensed matter physicist specializing in quantum materi
 als and many-body physics. He received his Ph.D. in Physics from the Unive
 rsity of Science and Technology of China (USTC) in 2021. He has carried ou
 t postdoctoral research at USTC\, The Pennsylvania State University\, and 
 The Hong Kong University of Science and Technology (HKUST)\, where he inve
 stigated emergent phenomena in quantum materials\, including unconventiona
 l superconductivity\, charge density waves\, ferroelectricity\, ultrafast 
 quantum dynamics\, and correlated electronic phases. His research focuses 
 on developing microscopic theories to understand the collective behaviors 
 and novel quantum states arising from strong interactions in quantum mater
 ials. \n\nhttps://indico-tdli.sjtu.edu.cn/event/5308/
LOCATION:Tsung-Dao Lee Institute/N6F-N600 - Lecture Room (Tsung-Dao Lee In
 stitute)
URL:https://indico-tdli.sjtu.edu.cn/event/5308/
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