261 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
Non-Abelian spin-orbit gauge: Persistent spin helix and quantum square ring
We re-express the Rashba and Dresselhaus interactions as non-Abelian
spin-orbit gauges and provide a new perspective in understanding the persistent
spin helix [Phys. Rev. Lett. 97, 236601 (2006)]. A spin-orbit interacting
system can be transformed into a free electron gas in the equal-strength
Rashba-Dresselhaus [001] linear model, the Dresselhaus [110] linear model, and
a one-dimensional system. A general tight-binding Hamiltonian for non-uniform
spin-orbit interactions and hoppings along arbitrary directions, within the
framework of finite difference method, is obtained. As an application based on
this Hamiltonian, a quantum square ring in contact with two ideal leads is
found to exhibit four states, insulating, spin-filtering, spin-flipping, and
spin-keeping states.Comment: 7 pages, 3 figure
Microwave-driven ferromagnet--topological-insulator heterostructures: The prospect for giant spin battery effect and quantized charge pump devices
We study heterostructures where a two-dimensional topological insulator (TI)
is attached to two normal metal (NM) electrodes while an island of a
ferromagnetic insulator (FI) with precessing magnetization covers a portion of
its lateral edges to induce time-dependent exchange field underneath via the
magnetic proximity effect. When the FI island covers both lateral edges, such
device pumps pure spin current in the absence of any bias voltage, thereby
acting as an efficient spin battery with giant output current even at very
small microwave power input driving the precession. When only one lateral edge
is covered by the FI island, both charge and spin current are pumped into the
NM electrodes. We delineate conditions for the corresponding conductances
(current-to-microwave-frequency ratio) to be quantized in a wide interval of
precession cone angles, which is robust with respect to weak disorder and can
be further extended by changes in device geometry.Comment: 7 pages, 7 color figures, PDFLaTe
Rashba Spin Interferometer
A spin interferometer utilizing the Rashba effect is proposed. The novel
design is composed of a one-dimensional (1D) straight wire and a 1D half-ring.
By calculating the norm of the superposed wave function, we derive analytical
expressions to describe the spin interference spectrum as a function of the
Rashba coupling strength. Presented spin interference results are identified to
include (i) the quantum-mechanical 4pi rotation effect, (ii) geometric effect,
and (iii) Shubnikov-de Haas-like beating effect.Comment: 3 pages, 3 figures, appears in the proceedings of the 10th Joint
MMM/Intermag Conferenc
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