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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-2922
DTSTART:20130131T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260412T170531Z
LAST-MODIFIED:20130116T212221Z
LOCATION:5310 Chamberlin
SUMMARY:Electronic Transport in Bi<sub>2</sub>Se<sub>3</sub> Thin Film
 s in the Topological Insulator Regime\, R. G. Herb Condensed Matter Se
 minar\, Dohun Kim\, University of Maryland
DESCRIPTION:The 3D topological insulators (TIs) have an insulating bul
 k but metallic surface states stemming from band inversion due to stro
 ng spin-orbit interaction\, whose existence is guaranteed by the topol
 ogy of the band structure of the insulator. Like graphene\, the STI su
 rface state generically has a Dirac electronic spectrum with massless 
 electrons and a vanishing bandgap at a Dirac point. In this talk\, I w
 ill discuss experiments on the TI material Bi<sub>2</sub>Se<sub>3</sub
 >\, which has a single topological Dirac surface state. Field effect t
 ransistors consisting of thin (5-17 nm) Bi<sub>2</sub>Se<sub>3</sub> a
 re fabricated by mechanical exfoliation of single crystals\, and elect
 rochemical and/or chemical gating methods are used to move the Fermi e
 nergy into the bulk bandgap\, revealing the ambipolar gapless nature o
 f transport in the Bi<sub>2</sub>Se<sub>3</sub> surface states [1]. Th
 e minimum conductivity of the topological surface state is understood 
 within the self-consistent theory of Dirac electrons in the presence o
 f charged impurities. The intrinsic finite-temperature resistivity of 
 the topological surface state due to electron-acoustic phonon scatteri
 ng is measured to be 60 times larger than that of graphene largely due
  to the smaller Fermi and sound velocities in Bi<sub>2</sub>Se<sub>3</
 sub> [2]\, which will have implications for topological electronic dev
 ices operating at room temperature. I will also discuss about our rece
 nt observation of 2D weak anti-localization (WAL) behavior in the low 
 field magneto transport\, which stems from topological surface states.
  By investigating gate-tuned WAL behaviors\, I will show that WAL in T
 I regime is extraordinarily sensitive to sub-meV coupling between top 
 and bottom topological surfaces\, and interplay of phase coherence tim
 e and inter surface tunneling time results interesting crossovers from
  coupled single channel to decoupled multichannel coherent transports.
 <br>
\n<br>
\n[1] D. Kim et al.\, <b><i>Nature Phys.</i> 8</b>\, 460 (
 2012).<br>
\n[2] D. Kim et al.\, <b><i>Phys. Rev. Lett.</i> 109</b>\, 
 166801 (2012).
URL:https://www.physics.wisc.edu/events/?id=2922
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