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PRODID:UW-Madison-Physics-Events
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SEQUENCE:1
UID:UW-Physics-Event-8163
DTSTART:20230207T160000Z
DTEND:20230207T170000Z
DTSTAMP:20260414T055032Z
LAST-MODIFIED:20230206T185645Z
LOCATION:5310 Chamberlin
SUMMARY:Building Tools for the Quantum Many-Body Problem: The Case of 
 Fractional Chern Insulators\, R. G. Herb Condensed Matter Seminar\, Da
 niel Parker \, Harvard
DESCRIPTION:The intermediate coupling regime of the quantum many-body 
 problem --- where kinetic and potential energy compete on the same ord
 er --- is notoriously difficult. Analytical approaches there are gener
 ically uncontrolled\, and numerical tools are often insufficient. Howe
 ver\, experiments on the growing array of two-dimensional materials ro
 utinely probe this regime. To understand such experiments\, a new inte
 rmediate coupling toolkit must be developed.
\n
\nThis talk will focus
  on recent experiments in magic-angle graphene that detected fractiona
 l Chern insulators. Fractional Chern insulators (FCIs) realize the rem
 arkable physics of the fractional quantum Hall effect in crystalline s
 ystems with Chern bands\, casting off the typical requirements of Land
 au levels and strong magnetic fields. Understanding these intermediate
 -coupling experiments required an "all of the above" approach\, combin
 ing close experimental collaborations with new theoretical and numeric
 al tools. I will start by briefly overviewing the experimental phenome
 nology: in small magnetic fields\, FCIs compete with charge-density wa
 ves due to the significant band dispersion. Next I will introduce ``vo
 rtexable bands"\, a class of beyond-Landau level systems with exact FC
 I ground states. Magic-angle graphene is vortexable in a limit\, makin
 g the realistic system almost ideal for FCIs. Finally\, I will use the
  new numerical technique of ``MPO compression" to compute the phase di
 agram of FCIs in magic-angle graphene\, predicting where experiments s
 hould look to find FCIs in zero external magnetic field. Future work w
 ill study pairs of Chern bands related by time-reversal symmetry that\
 , instead of FCIs\, naturally host superconductors.
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URL:https://www.physics.wisc.edu/events/?id=8163
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