3,770 research outputs found
Spin Polarization Dependence of Carrier Effective Mass in Semiconductor Structures: Spintronic Effective Mass
We introduce the concept of a spintronic effective mass for spin-polarized
carriers in semiconductor structures, which arises from the strong
spin-polarization dependence of the renormalized effective mass in an
interacting spin-polarized electron system. The majority-spin many-body
effective mass renormalization differs by more than a factor of 2 at rs=5
between the unpolarized and the fully polarized two-dimensional system, whereas
the polarization dependence (~15%) is more modest in three dimensions around
metallic densities (rs~5). The spin-polarization dependence of the carrier
effective mass is of significance in various spintronic applications.Comment: Final versio
Spin Bose Glass Phase in Bilayer Quantum Hall Systems at
We develop an effective spin theory to describe magnetic properties of the
Quantum Hall bilayer systems. In the absence of disorder this theory
gives quantitative agreement with the results of microscopic Hartree-Fock
calculations, and for finite disorder it predicts the existence of a novel spin
Bose glass phase. The Bose glass is characterized by the presence of domains of
canted antiferromagnetic phase with zero average antiferromagnetic order and
short range mean antiferromagnetic correlations. It has infinite
antiferromagnetic transverse susceptibility, finite longitudinal spin
susceptibility and specific heat linear in temperature. Transition from the
canted antiferromagnet phase to the spin Bose glass phase is characterized by a
universal value of the longitudinal spin conductance.Comment: 4 pages, 4 eps figure
Edge Transport in 2D Cold Atom Optical Lattices
We theoretically study the observable response of edge currents in two
dimensional cold atom optical lattices. As an example we use Gutzwiller
mean-field theory to relate persistent edge currents surrounding a Mott
insulator in a slowly rotating trapped Bose-Hubbard system to time of flight
measurements. We briefly discuss an application, the detection of Chern number
using edge currents of a topologically ordered optical lattice insulator
Chirality in Quantum Computation with Spin Cluster Qubits
We study corrections to the Heisenberg interaction between several lateral,
single-electron quantum dots. We show, using exact diagonalization, that
three-body chiral terms couple triangular configurations to external sources of
flux rather strongly. The chiral corrections impact single qubit encodings
utilizing loops of three or more Heisenberg coupled quantum dots.Comment: 5 pages, 2 figure
Charged impurity scattering limited low temperature resistivity of low density silicon inversion layers
We calculate within the Boltzmann equation approach the charged impurity
scattering limited low temperature electronic resistivity of low density
-type inversion layers in Si MOSFET structures. We find a rather sharp
quantum to classical crossover in the transport behavior in the K
temperature range, with the low density, low temperature mobility showing a
strikingly strong non-monotonic temperature dependence, which may qualitatively
explain the recently observed anomalously strong temperature dependent
resistivity in low-density, high-mobility MOSFETs.Comment: 5 pages, 2 figures, will appear in PRL (12 July, 1999
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
Intrinsic Spin Hall Effect in the presence of Extrinsic Spin-Orbit Scattering
Intrinsic and extrinsic spin Hall effects are considered together on an equal
theoretical footing for the Rashba spin-orbit coupling in two-dimensional (2D)
electron and hole systems, using the diagrammatic method for calculating the
spin Hall conductivity. Our analytic theory for the 2D holes shows the expected
lowest-order additive result for the spin Hall conductivity. But, the 2D
electrons manifest a very surprising result, exhibiting a non-analyticity in
the Rashba coupling strength where the strictly extrinsic spin Hall
conductivity (for ) cannot be recovered from the
limit of the combined theory. The theoretical results are discussed in the
context of existing experimental results.Comment: 5 pages, 2 figure
Controls of dimethyl sulphide in the Bay of Bengal during BOBMEX-Pilot cruise 1998
The air-sea exchange is one of the main mechanisms maintaining the abundances of trace gases in the atmosphere. Some of these, such as carbon dioxide and dimethyl sulphide (DMS), will have a bearing on the atmospheric heat budget. While the former facilitates the trapping of radiation (greenhouse effect) the latter works in the opposite direction through reflectance of radiation back into space by sulphate aerosols that form from oxidation of DMS in atmosphere. Here we report on the first measurements made on DMS in the Bay of Bengal and the factors regulating its abundance in seawater. Phytoplankton alone does not seem to control the extent of DMS concentrations. We find that changes in salinity could effectively regulate the extent of DMSP production by marine phytoplankton. In addition, we provide the first ever evidence to the occurrence of DMS precursor, DMSP, in marine aerosols collected in the boundary layer. This suggests that the marine aerosol transport of DMSP will supplement DMS gaseous evasion in maintaining the atmospheric non-sea salt sulphur budget
Time-reversal symmetry breaking by a density-wave state in underdoped cuprate superconductors
It was proposed that the density-wave state (DDW) may be
responsible for the pseudogap behavior in the underdoped cuprates. Here we show
that the admixture of a small component to the DDW state breaks the
symmetry between the counter-propagating orbital currents of the DDW state and,
thus, violates the macroscopic time-reversal symmetry. This symmetry breaking
results in a non-zero polar Kerr effect, which has recently been observed in
the pseudogap phase.Comment: 4 pages, 3 eps figures; minor typos corrected, references updated,
new title as suggested by the PRL editor; references updated, final version
as published in PR
The Exchange Gate in Solid State Spin Quantum Computation: The Applicability of the Heisenberg Model
Solid state quantum computing proposals rely on adiabatic operations of the
exchange gate among localized spins in nanostructures. We study corrections to
the Heisenberg interaction between lateral semiconductor quantum dots in an
external magnetic field. Using exact diagonalization we obtain the regime of
validity of the adiabatic approximation. We also find qualitative corrections
to the Heisenberg model at high magnetic fields and in looped arrays of spins.
Looped geometries of localized spins generate flux dependent, multi-spin terms
which go beyond the basic Heisenberg model.Comment: 13 pages, 8 figure
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