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X-WR-CALNAME;VALUE=TEXT:Department of Physics
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DTSTART:20191103T020000
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DTSTART:20190310T020000
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UID:calendar.9671.field_events_date.0@phy.princeton.edu
DTSTAMP:20190823T170349Z
CREATED:20190813T152955Z
DESCRIPTION:The quantum Hall effect encompasses a large variety of phases a
nd phenomena arising from the combination of topological bands (the Landau
levels)\, strong electron-electron interactions\, and disorder. This thes
is consists of an in-depth numerical study of some of these fascinating ph
enomena.\n\nIn the first part\, we study the effect of geometric distortio
ns of the underlying electron band on fractional quantum Hall (FQH) and co
mposite Fermi liquid (CFL) states in the lowest Landau level (LLL). Throug
h extensive density matrix renormalization group numerical simulations\, w
e map the shape of correlations in both types of states in the presence of
band mass anisotropy. We find that the geometry of FQH states depends on
the LLL filling fraction\, in agreement with a microscopic model of flux a
ttachment. At half filling\, the system forms a gapless CFL state with an
emergent Fermi contour. We quantify its anisotropy and compare it to that
of the zero-field carriers\, finding an approximate square-root relationsh
ip between the two which is in excellent agreement with concurrent experim
ents on strained GaAs quantum wells. In contrast\, we find the CFL Fermi c
ontour is very weakly affected by other types of band distortions.\n\nThe
second part of the thesis investigates quantum phase transitions in the LL
L. We focus first on the integer quantum Hall plateau transition for disor
dered\, non-interacting electrons. We study this transition in the presenc
e of point impurities which remove a fraction of the states from the Landa
u band without altering its topological character. We then characterize th
e quasi-one dimensional limit of the transition\, which reveals a surprisi
ng interplay between topology and disorder. We conclude with a study of qu
antum criticality in graphene Landau levels for clean\, interacting electr
ons\, focusing on a critical point between an antiferromagnet and a valenc
e bond solid which is conjectured to exhibit `deconfined' quantum critical
ity.\n\n
DTSTART;TZID=America/New_York:20190827T110000
DTEND;TZID=America/New_York:20190827T110000
LAST-MODIFIED:20190813T152955Z
LOCATION:Jadwin Hall - Chair's Conference Room 202
SUMMARY:FPO - Matteo Ippoliti - Geometric distortions and quantum criticali
ty in the lowest Landau level
URL;TYPE=URI:https://phy.princeton.edu/events/fpo-matteo-ippoliti-geometric
-distortions-and-quantum-criticality-lowest-landau-level
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