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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2851
DTSTART:20121220T160000Z
DURATION:PT1H0M0S
DTSTAMP:20240319T135601Z
LAST-MODIFIED:20121116T213108Z
LOCATION:5310 Chamberlin
SUMMARY:Electronic Transport in Bi2Se3 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 Bi2Se3\, which has a single topological Dirac surface state. Field effect t
ransistors consisting of thin (5-17 nm) Bi2Se3 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 Bi2Se3 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 Bi2Se3
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.
\n
\n[1] D. Kim et al.\, Nature Phys. 8\, 460 (
2012).
\n[2] D. Kim et al.\, Phys. Rev. Lett. 109\,
166801 (2012).
URL:https://www.physics.wisc.edu/events/?id=2851
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