35 research outputs found
Intrinsic Electron-Phonon Resistivity in Bi2Se3 in the Topological Regime
We measure the temperature-dependent carrier density and resistivity of the
topological surface state of thin exfoliated Bi2Se3 in the absence of bulk
conduction. When the gate-tuned chemical potential is near or below the Dirac
point the carrier density is strongly temperature dependent reflecting thermal
activation from the nearby bulk valence band, while above the Dirac point,
unipolar n-type surface conduction is observed with negligible thermal
activation of bulk carriers. In this regime linear resistivity vs. temperature
reflects intrinsic electron-acoustic phonon scattering. Quantitative comparison
with a theoretical transport calculation including both phonon and disorder
effects gives the ratio of deformation potential to Fermi velocity D/\hbarvF =
4.7 {\AA}-1. This strong phonon scattering in the Bi2Se3 surface state gives
intrinsic limits for the conductivity and charge carrier mobility at room
temperature of ~550 {\mu}S per surface and ~10,000 cm2/Vs.Comment: 15 pages, 3 figures, minor revision (version 2
Insulating behavior in ultra-thin bismuth selenide field effect transistors
Ultrathin (~3 quintuple layer) field-effect transistors (FETs) of topological
insulator Bi2Se3 are prepared by mechanical exfoliation on 300nm SiO2/Si
susbtrates. Temperature- and gate-voltage dependent conductance measurements
show that ultrathin Bi2Se3 FETs are n-type, and have a clear OFF state at
negative gate voltage, with activated temperature-dependent conductance and
energy barriers up to 250 meV
Topological insulator quantum dot with tunable barriers
Thin (6-7 quintuple layer) topological insulator Bi2Se3 quantum dot devices
are demonstrated using ultrathin (2~4 quintuple layer) Bi2Se3 regions to
realize semiconducting barriers which may be tuned from Ohmic to tunneling
conduction via gate voltage. Transport spectroscopy shows Coulomb blockade with
large charging energy >5 meV, with additional features implying excited states
C -Axis Transport in Ute2: Evidence of Three-Dimensional Conductivity Component
We study the temperature dependence of electrical resistivity for currents directed along all crystallographic axes of the spin-triplet superconductor UTe2. We focus particularly on an accurate determination of the resistivity along the c axis (ρc) by using a generalized Montgomery technique that allows extraction of crystallographic resistivity components from a single sample. In contrast to expectations from the observed highly anisotropic band structure, our measurement of the absolute values of resistivities in all current directions reveals a surprisingly nearly isotropic transport behavior at temperatures above Kondo coherence, with ρc∼ρb∼2ρa, that evolves to reveal qualitatively distinct behaviors on cooling. The temperature dependence of ρc exhibits a peak at a temperature much lower than the onset of Kondo coherence observed in ρa and ρb, consistent with features in magneto transport and magnetization that point to a magnetic origin. A comparison to the temperature-dependent evolution of the scattering rate observed in angle-resolved photoemission spectroscopy experiments provides important insights into the underlying electronic structure necessary for building a microscopic model of superconductivity in UTe2
Astonish Me! Recalling the Cabaret Spirit
Program for the 1999 RISD Wintersessoin Cabaret intiated by the Image and Word class in collaboration with students of RISD Cabaret 1998 and held at AS220. The presentation was conceived and performed in homage and celebration of past RISD Cabaret shows 1987-1998. Graphic Design: Ron Winter, Ji-Ho Sohn and Eric Urban.https://digitalcommons.risd.edu/liberalarts_cabaret_programs/1010/thumbnail.jp