659 research outputs found
Magnetotransport in a time-modulated double quantum point contact system
We report on a time-dependent Lippmann-Schwinger scattering theory that
allows us to study the transport spectroscopy in a time-modulated double
quantum point contact system in the presence of a perpendicular magnetic field.
Magnetotransport properties involving inter-subband and inter-sideband
transitions are tunable by adjusting the time-modulated split-gates and the
applied magnetic field. The observed magnetic field induced Fano resonance
feature may be useful for the application of quantum switching.Comment: 3 pages, 4 figure
Flatland Electrons in High Magnetic Fields
This paper provides a review of developments in the physics of
two-dimensional electron systems in perpendicular magnetic fields.Comment: Review paper, to be published in book series "High Magnetic Fields:
Science and Technology" edited by Fritz Herlach and Noboru Miura, World
Scientific C
The Role of Alternance Symmetry in Magnetoconductance
We show that the direction of coherent electron transport across a cyclic
system of quantum dots or a cyclic molecule can be modulated by an external
magnetic field if the cycle has an odd number of hopping sites, but the
transport becomes completely symmetric if the number is even. These contrasting
behaviors, which remain in the case of interacting electrons, are a consequence
of the absence or presence of alternance symmetry in the system. These findings
are relevant for the design of nanocircuits based on coupled quantum dots or
molecular junctions.Comment: to be published in PR
Gate-dependent magnetoresistance phenomena in carbon nanotubes
We report on the first experimental study of the magnetoresistance of double-walled carbon nanotubes under magnetic field as large as 50 Tesla. By varying the field orientation with respect to the tube axis, or by gate-mediated shifting the Fermi level position, evidences for unconventional magnetoresistance are presented and interpreted by means of theoretical calculations
Efficient quantum transport simulation for bulk graphene heterojunctions
The quantum transport formalism based on tight-binding models is known to be
powerful in dealing with a wide range of open physical systems subject to
external driving forces but is, at the same time, limited by the memory
requirement's increasing with the number of atomic sites in the scattering
region. Here we demonstrate how to achieve an accurate simulation of quantum
transport feasible for experimentally sized bulk graphene heterojunctions at a
strongly reduced computational cost. Without free tuning parameters, we show
excellent agreement with a recent experiment on Klein backscattering [A. F.
Young and P. Kim, Nature Phys. 5, 222 (2009)].Comment: 5 pages, 3 figure
Single-Electron Effects in a Coupled Dot-Ring System
Aharonov-Bohm oscillations are studied in the magnetoconductance of a
micron-sized open quantum ring coupled capacitively to a Coulomb-blockaded
quantum dot. As the plunger gate of the dot is modulated and tuned through a
conductance resonance, the amplitude of the Aharonov-Bohm oscillations in the
transconductance of the ring displays a minimum. We demonstrate that the effect
is due to a single-electron screening effect, rather than to dephasing.
Aharonov-Bohm oscillations in a quantum ring can thus be used for the detection
of single charges.Comment: 5 pages, 3 figure
Charge metastability and hysteresis in the quantum Hall regime
We report simultaneous quasi-dc magnetotransport and high frequency surface
acoustic wave measurements on bilayer two-dimensional electron systems in GaAs.
Near strong integer quantized Hall states a strong magnetic field sweep
hysteresis in the velocity of the acoustic waves is observed at low
temperatures. This hysteresis indicates the presence of a metastable state with
anomalously high conductivity in the interior of the sample. This
non-equilibrium state is not revealed by conventional low frequency transport
measurements which are dominated by dissipationless transport at the edge of
the 2D system. We find that a field-cooling technique allows the equilibrium
charge configuration within the interior of the sample to be established. A
simple model for this behavior is discussed.Comment: 8 pages, 4 postscript figure
Landau-Zener-Stuckelberg-Majorana interferometry of a single hole
We perform Landau-Zener-Stuckelberg-Majorana (LZSM) spectroscopy on a system
with strong spin-orbit interaction (SOI), realized as a single hole confined in
a gated double quantum dot. In analogy to the electron systems, at magnetic
field B=0 and high modulation frequencies we observe the photon-assisted
tunneling (PAT) between dots, which smoothly evolves into the typical LZSM
funnel-shaped interference pattern as the frequency is decreased. In contrast
to electrons, the SOI enables an additional, efficient spin-flipping interdot
tunneling channel, introducing a distinct interference pattern at finite B.
Magneto-transport spectra at low-frequency LZSM driving show the two channels
to be equally coherent. High-frequency LZSM driving reveals complex
photon-assisted tunneling pathways, both spin-conserving and spin-flipping,
which form closed loops at critical magnetic fields. In one such loop an
arbitrary hole spin state is inverted, opening the way toward its
all-electrical manipulation.Comment: 6 pages, 4 figures, and supplementary materia
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