942 research outputs found
Anomalous spin Hall effects in Dresselhaus (110) quantum wells
Anomalous spin Hall effects that belong to the intrinsic type in Dresselhaus
(110) quantum wells are discussed. For the out-of-plane spin component,
antisymmetric current-induced spin polarization induces opposite spin Hall
accumulation, even though there is no spin-orbit force due to Dresselhaus (110)
coupling. A surprising feature of this spin Hall induction is that the spin
accumulation sign does not change upon bias reversal. Contribution to the spin
Hall accumulation from the spin Hall induction and the spin deviation due to
intrinsic spin-orbit force as well as extrinsic spin scattering, can be
straightforwardly distinguished simply by reversing the bias. For the inplane
component, inclusion of a weak Rashba coupling leads to a new type of
intrinsic spin Hall effect solely due to spin-orbit-force-driven spin
separation.Comment: 6 pages, 5 figure
Switching off the magnetic exchange coupling by quantum resonances
We clarify the role of quantum-well states in magnetic trilayer systems from
majority carrier in the ferromagnetic and all carriers in the antiferromagnetic
configurations. In addition to numerical and analytic calculations, heuristic
pictures are provided to explain effects of a capping layer and side-layer
modulation in recent experiments. This immediately offers answers to two
unexplained subtle findings in experiments and band-structure calculations,
individually. Furthermore, it allows a more flexible tuning of or even turning
off the interlayer exchange coupling.Comment: 5 pages, 5 figure
Strongly anisotropic ballistic magnetoresistance in compact three-dimensional semiconducting nanoarchitectures
We establish theoretically that in nonmagnetic semiconducting bilayer or
multilayer thin film systems rolled up into compact quasi-one-dimensional
nanoarchitectures, the ballistic magnetoresistance is very anisotropic:
conductances depend strongly on the direction of an externally applied magnetic
field. This phenomenon originates from the curved open geometry of rolled-up
nanotubes, which leads to a tunability of the number of quasi-one-dimensional
magnetic subbands crossing the Fermi energy. The experimental significance of
this phenomenon is illustrated by a sizable anisotropy that scales with the
inverse of the winding number, and persists up to a critical temperature that
can be strongly enhanced by increasing the strength of the external magnetic
field or the characteristic radius of curvature, and can reach room
temperature.Comment: 5 pages, 4 figures, one supplemental materia
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Theoretical Prediction of a Giant Anisotropic Magnetoresistance in Carbon Nanoscrolls
Snake orbits are trajectories of charge carriers curving back and forth that form at an interface where either the magnetic field direction or the charge carrier type are inverted. In ballistic samples, their presence is manifested in the appearance of magnetoconductance oscillations at small magnetic fields. Here we show that signatures of snake orbits can also be found in the opposite diffusive transport regime. We illustrate this by studying the classical magnetotransport properties of carbon tubular structures subject to relatively weak transversal magnetic fields where snake trajectories appear in close proximity to the zero radial field projections. In carbon nanoscrolls, the formation of snake orbits leads to a strongly directional dependent positive magnetoresistance with an anisotropy up to 80%
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