3,544 research outputs found
Quantum Schur Superalgebras and Kazhdan-Lusztig Combinatorics
We introduce the notion of quantum Schur (or -Schur) superalgebras. These
algebras share certain nice properties with -Schur algebras such as base
change property, existence of canonical -bases, and the
duality relation with quantum matrix superalgebra \sA(m|n). We also construct
a cellular \mathbb Q(\up)-basis and determine its associated cells, called
super-cells, in terms of a Robinson--Schensted--Knuth super-correspondence. In
this way, we classify all irreducible representations over \mathbb Q(\up) via
super-cell modules.Comment: 31 page
Evidence for Helical Edge Modes in Inverted InAs/GaSb Quantum Wells
We present an experimental study of low temperature electronic transport in
the hybridization gap of inverted InAs/GaSb composite quantum wells.
Electrostatic gate is used to push the Fermi level into the gap regime, where
the conductance as a function of sample length and width is measured. Our
analysis shows strong evidence for the existence of helical edge modes proposed
by Liu et al [Phys. Rev. Lett., 100, 236601 (2008)]. Edge modes persist inspite
of sizable bulk conduction and show only a weak magnetic field dependence - a
direct consequence of gap opening away from zone center.Comment: 4 pages, 4 figure
Perfect Andreev Reflection of Helical Edge Modes in InAs/GaSb Quantum Wells
We present an experimental study of inverted InAs/GaSb composite quantum
wells in the hybridization regime and contacted by superconducting electrodes.
A front gate is used to vary the Fermi level into the mini-gap, where recent
experiments indicate existence of helical edge modes [arXiv:1105.0137]. Zero
bias dips in differential resistance are observed across the mini-gap,
suggesting transport dominated by Andreev reflection processes. Evolution of
the mini-gap differential resistance with applied bias as well as measured
mini-gap excess current of 150 nA are in good agreement with the prediction of
perfect Andreev reflection of the helical edge modes, which is necessitated by
the absence of back-scattering channels. The perfect Andreev reflection occurs
in spite of a finite barrier at the interface and shows strong sensitivity to
time-reversal breaking - hallmarks of the helical nature of quantum spin Hall
edges
Simultaneous Measurements of Microwave Photoresistance and Cyclotron Reflection in the Multi-Photon Regime
We simultaneously measure photoresistance with electrical transport and
plasmon-cyclotron resonance (PCR) using microwave reflection spectroscopy in
high mobility GaAs/AlGaAs quantum wells under a perpendicular magnetic field.
Multi-photon transitions are revealed as sharp peaks in the resistance and the
cyclotron reflection on samples with various carrier densities. Our main
finding is that plasmon coupling is relevant in the cyclotron reflection
spectrum but has not been observed in the electrical conductivity signal. We
discuss possible mechanisms relevant to reflection or dc conductivity signal to
explain this discrepancy. We further confirm a trend that higher order
multi-photon features can be observed using higher carrier density samples.Comment: 19 pages, 5 figure
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