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DTSTART;TZID=America/New_York:20231018T123000
DTEND;TZID=America/New_York:20231018T133000
DTSTAMP:20240223T113334Z
CREATED:20240223T113304Z
LAST-MODIFIED:20240223T113334Z
UID:10002866-1697632200-1697635800@cmsa.fas.harvard.edu
SUMMARY:Composite fermions and the fractional quantum anomalous Hall effect
DESCRIPTION:Topological Quantum Matter Seminar \nSpeaker: Hart Goldman\, University of Chicago \nTitle: Composite fermions and the fractional quantum anomalous Hall effect \nAbstract: Recent experiments have revealed evidence for fractional quantum anomalous Hall (FQAH) states at zero magnetic field in a growing number of moire materials. In this talk\, I will argue that a composite fermion description\, already a unifying framework for the phenomenology of 2d electron gases at high magnetic fields\, provides a similarly powerful perspective in this new zero-field context. In particular\, a central prediction of the composite fermion framework is a non-Fermi liquid metal of composite fermions at even-denominator fillings. To this end\, I will present exact diagonalization evidence for such composite Fermi liquid states at zero magnetic field in twisted MoTe2 bilayers\, at fillings n = 1/2 and n = 3/4. Dubbing these states anomalous composite Fermi liquids (ACFLs)\, I will argue that they play a central organizing role in the FQAH phase diagram. I will also develop a long wavelength theory for this ACFL state\, which offers concrete experimental predictions that I will discuss in relation to current measurements. For example\, upon doping the composite Fermi sea\, one obtains a Jain sequence of FQAH states consistent with those observed experimentally\, as well as a new type of commensurability oscillations originating from the superlattice potential intrinsic to the system. Finally\, I will discuss opportunities for new physics not possible in quantum Hall systems at finite magnetic field.
URL:https://cmsa.fas.harvard.edu/event/tqms_101823/
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-10.18.23.png
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