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PRODID:UW-Madison-Physics-Events
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UID:UW-Physics-Event-2687
DTSTART:20120913T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260420T021613Z
LAST-MODIFIED:20120904T124812Z
LOCATION:5310 Chamberlin
SUMMARY:Competing Phases of 2D Electrons at ν = 5/2 and 7/3 in frac
 tional quantum Hall systems\, R. G. Herb Condensed Matter Seminar\, Ji
 ng Xia\, University of California - Irvine
DESCRIPTION:In 2 dimensional electron systems (2DES) in GaAs/AlGaAs qu
 antum wells\, the N=1 Landau level (LL) exhibits collective electronic
  phenomena characteristic of both fractional quantum Hall (FQHE) state
 s seen in the lowest LL and anisotropic nematic states in the higher L
 Ls. In particular\, fractional quantum Hall effect (FQHE) at I1/2 = 5/
 2 (and 7/2) is thought to obey non-Abelian statistics and holds the pr
 omise of realizing topologically protected quantum computers. Intrigui
 ngly\, a modest in-plane magnetic field B|| is sufficient to destroy t
 he FQH states at I1/2 = 5/2 (and 7/2) and replace them with anisotropi
 c compressible nematic phases\, revealing the close competition betwee
 n the two. We find that at larger B|| these anisotropic phases I1/2 = 
 5/2 can themselves be replaced by a new isotropic state\, dubbed re-en
 trant isotropic compressible (RIC) phase [1]. We present strong eviden
 ce that this transition is a consequence of the mixing of Landau level
 s from different electric subbands in the confinement potential. In ad
 dition\, we find that with B||\, the normally isotropic I1/2 = 7/3 FQH
 E state can transform into an anisotropic phase with an accurately qua
 ntized Hall plateau but an anisotropic longitudinal resistivitiescite 
 [2]. As temperature is lowered towards zero\, Ixx diminishes while Iyy
  tends to diverge\, reminiscent of the anisotropic nematic states\, wh
 ile surprisingly Ixy and Iyx remain quantized at 3h/7e2\, indicating a
  completely new quantum phase.<br>
\n<br>
\nReferences: <br>
\n[1]	J. 
 Xia\, V. Cvicek\, J. P. Eisenstein\, L. N. Pfeiffer\, and K. W. West\,
  Phys Rev Lett 105\, 176807 (2010).<br>
\n[1]	J. Xia\, J. P. Eisenstei
 n\, L. N. Pfeiffer\, and K. W. West\, Nature Physics (2011).
URL:https://www.physics.wisc.edu/events/?id=2687
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