1,188 research outputs found
Theory of spin, electronic and transport properties of the lateral triple quantum dot molecule in a magnetic field
We present a theory of spin, electronic and transport properties of a
few-electron lateral triangular triple quantum dot molecule in a magnetic
field. Our theory is based on a generalization of a Hubbard model and the
Linear Combination of Harmonic Orbitals combined with Configuration Interaction
method (LCHO-CI) for arbitrary magnetic fields. The few-particle spectra
obtained as a function of the magnetic field exhibit Aharonov-Bohm
oscillations. As a result, by changing the magnetic field it is possible to
engineer the degeneracies of single-particle levels, and thus control the total
spin of the many-electron system. For the triple dot with two and four
electrons we find oscillations of total spin due to the singlet-triplet
transitions occurring periodically in the magnetic field. In the three-electron
system we find a transition from a magnetically frustrated to the
spin-polarized state. We discuss the impact of these phase transitions on the
addition spectrum and the spin blockade of the lateral triple quantum dot
molecule.Comment: 30 pages (one column), 9 figure
Wave attenuation and dispersion due to floating ice covers
Experiments investigating the attenuation and dispersion of surface waves in
a variety of ice covers are performed using a refrigerated wave flume. The ice
conditions tested in the experiments cover naturally occurring combinations of
continuous, fragmented, pancake and grease ice. Attenuation rates are shown to
be a function of ice thickness, wave frequency, and the general rigidity of the
ice cover. Dispersion changes were minor except for large wavelength increases
when continuous covers were tested. Results are verified and compared with
existing literature to show the extended range of investigation in terms of
incident wave frequency and ice conditions
A Reconfigurable Gate Architecture for Si/SiGe Quantum Dots
We demonstrate a reconfigurable quantum dot gate architecture that
incorporates two interchangeable transport channels. One channel is used to
form quantum dots and the other is used for charge sensing. The quantum dot
transport channel can support either a single or a double quantum dot. We
demonstrate few-electron occupation in a single quantum dot and extract
charging energies as large as 6.6 meV. Magnetospectroscopy is used to measure
valley splittings in the range of 35-70 microeV. By energizing two additional
gates we form a few-electron double quantum dot and demonstrate tunable tunnel
coupling at the (1,0) to (0,1) interdot charge transition.Comment: Related papers at http://pettagroup.princeton.ed
Direct control of the tunnel splitting in a one-electron double quantum dot
Quasi-static transport measurements are employed on a laterally defined
tunnel-coupled double quantum dot. A nearby quantum point contact allows us to
track the charge as added to the device. If charged with only up to one
electron, the low-energy spectrum of the double quantum dot is characterized by
its quantum mechanical interdot tunnel splitting. We directly measure its
magnitude by utilizing particular anticrossing features in the stability
diagram at finite source-drain bias. By modification of gate voltages defining
the confinement potential as well as by variation of a perpendicular magnetic
field we demonstrate the tunability of the coherent tunnel coupling.Comment: High resolution pdf file available at
http://www2.nano.physik.uni-muenchen.de/~huettel/research/anticrossing.pd
Parallel magnetic field induced giant magnetoresistance in low density {\it quasi}-two dimensional layers
We provide a possible theoretical explanation for the recently observed giant
positive magnetoresistance in high mobility low density {\it quasi}-two
dimensional electron and hole systems. Our explanation is based on the strong
coupling of the parallel field to the {\it orbital} motion arising from the
{\it finite} layer thickness and the large Fermi wavelength of the {\it
quasi}-two dimensional system at low carrier densities.Comment: 4 pages with 4 figures. Accepted for Publication in Physical Review
Letter
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