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DTSTART;TZID=America/New_York:20230913T103000
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DTSTAMP:20260420T095248
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UID:10001122-1694601000-1694604600@cmsa.fas.harvard.edu
SUMMARY:Phase transitions out of quantum Hall states in moire TMD bilayers
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Xueyang Song (MIT) \nTitle: Phase transitions out of quantum Hall states in moire TMD bilayers \nAbstract: Motivated by the recent experimental breakthroughs in observing Fractional Quantum Anomalous Hall (FQAH) states in moir\’e Transition Metal Dichalcogenide (TMD) bilayers\, we propose and study various unconventional phase transitions between quantum Hall phases and Fermi liquids or charge ordered phases upon tuning the bandwidth.  At filling -2/3\, we describe a direct transition between the FQAH state and a Charge Density Wave (CDW) insulator. The critical theory resembles that of the familiar deconfined quantum critical point (DQCP) but with an additional Chern-Simons term. At filling -1/2\, we study the possibility of a continuous transition between the composite Fermi liquid (CFL) and the Fermi liquid (FL) building on and refining previous work by  Barkeshli and McGreevy.   Crucially we show that translation symmetry alone is enough to enable a second order CFL-FL transition. We argue that there must be critical CDW fluctuations though neither phase has long range CDW order.  A striking signature is a universal jump of resistivities at the critical point. With disorder\, we argue that the CDW order gets pinned and the CFL-FL evolution happens through an intermediate electrically insulating phase with mobile neutral fermions. A clean analog of this insulating phase with long range CDW order and a neutral fermi surface can potentially also exist.  We also present a critical theory for the CFL to FL transition at filling -3/4.  Our work opens up a new avenue to realize deconfined criticality and fractionalized phases beyond familiar Landau level physics in the moire Chern band system.
URL:https://cmsa.fas.harvard.edu/event/tqms_91323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Topological Quantum Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-09.12.23.docx-2.png
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DTSTART;TZID=America/New_York:20230913T163000
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CREATED:20240223T111403Z
LAST-MODIFIED:20240223T111403Z
UID:10002859-1694622600-1694628000@cmsa.fas.harvard.edu
SUMMARY:Anomalies of Non-Invertible Symmetries
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Clay Córdova (U Chicago) \nTitle: Anomalies of Non-Invertible Symmetries
URL:https://cmsa.fas.harvard.edu/event/qm_91323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.13.23.png
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