771 research outputs found
Spin transverse force and quantum transverse transport
We present a brief review on spin transverse force, which exerts on the spin
as the electron is moving in an electric field. This force, analogue to the
Lorentz force on electron charge, is perpendicular to the electric field and
spin current carried by the electron. The force stems from the spin-orbit
coupling of electrons as a relativistic quantum effect, and could be used to
understand the Zitterbewegung of electron wave packet and the quantum
transverse transport of electron in a heuristic way.Comment: 4 pages, manuscript of invited talk on IAS Workshop on Spintronics at
Nanyang Techological University, Singapore, 200
Spin transverse force and intrinsic quantum transverse transport
The spin-orbit coupling may generate spin transverse force on moving electron
spin, which gives a heuristic picture for the quantum transverse transport of
electron. A relation between the spin and anomalous Hall conductance and spin
force was established, and applied to several systems. It was predicted that
the sign change of anomalous Hall conductance can occur in diluted magnetic
semiconductors of narrow band and can be applied to identify intrinsic
mechanism experimentally
Theory of magnetoelectric photocurrent generated by direct interband transitions in semiconductor quantum well
A linearly polarized light normally incident on a semiconductor quantum well
with spin-orbit coupling may generate pure spin current via direct interband
optical transition. An electric photocurrent can be extracted from the pure
spin current when an in-plane magnetic field is applied, which has been
recently observed in the InGaAs/InAlAs quantum well [Dai et al., Phys. Rev.
Lett. 104, 246601 (2010)]. Here we present a theoretical study of this
magnetoelectric photocurrent effect associated with the interband transition.
By employing the density matrix formalism, we show that the photoexcited
carrier density has an anisotropic distribution in k space, strongly dependent
on the orientation of the electron wavevector and the polarization of the
light. This anisotropy provides an intuitive picture of the observed dependence
of the photocurrent on the magnetic field and the polarization of the light. We
also show that the ratio of the pure spin photocurrent to the magnetoelectric
photocurrent is approximately equal to the ratio of the kinetic energy to the
Zeeman energy, which enables us to estimate the magnitude of the pure spin
photocurrent. The photocurrent density calculated with the help of an
anisotropic Rashba model and the Kohn-Luttinger model can produce all three
terms in the fitting formula for measured current, with comparable order of
magnitude, but discrepancies are still present and further investigation is
needed.Comment: 13 pages, 9 figures, 2 table
Crossover from Majorana edge to end states in quasi-one-dimensional p-wave superconductors
In a recent work [Potter and Lee, Phys. Rev. Lett. 105, 227003 (2010)], it
was demonstrated by means of numerical diagonalization that the Majorana end
states can be localized at opposite ends of a sample of an ideal spinless
p-wave superconductor with the strip geometry beyond the strict one-dimensional
limit. Here we reexamine this issue, and study the topological quantum phase
transition in the same system. We give the phase diagrams of the presence of
Majorana end modes by using of topological index. It is found that the
topological property of a strip geometry will change in an oscillatory way with
respect of the sample width.Comment: 8 pages, 5 figure
Spin-bias driven magnetization reversal and nondestructive detection in a single molecular magnet
The magnetization reversal in a single molecular magnet (SMM) weakly coupled
to an electrode with spin-dependent splitting of chemical potentials (spin
bias) is theoretically investigated by means of the rate equation. A
microscopic mechanism for the reversal is demonstrated by the avalanche
dynamics at the reversal point. The magnetization as a function of the spin
bias shows hysteresis loops tunable by the gate voltage and varying with
temperature. The nondestructive measurement to the orientation of giant spin in
SMM is presented by measuring the fully polarized electric current in the
response to a small spin bias. For Mnac molecule, its small transverse
anisotropy only slightly violates the results above. The situation when there
is an angle between the easy axis of the SMM and the spin quantization
direction of the electrode is also studied.Comment: 17 pages, 12 figure
Exposure of the Hidden Anti-Ferromagnetism in Paramagnetic CdSe:Mn Nanocrystals
We present theoretical and experimental investigations of the magnetism of
paramagnetic semiconductor CdSe:Mn nanocrystals and propose an efficient
approach to the exposure and analysis of the underlying anti-ferromagnetic
interactions between magnetic ions therein. A key advance made here is the
build-up of an analysis method with the exploitation of group theory technique
that allows us to distinguish the anti-ferromagnetic interactions between
aggregative Mn2+ ions from the overall pronounced paramagnetism of magnetic ion
doped semiconductor nanocrystals. By using the method, we clearly reveal and
identify the signatures of anti-ferromagnetism from the measured temperature
dependent magnetisms, and furthermore determine the average number of Mn2+ ions
and the fraction of aggregative ones in the measured CdSe:Mn nanocrystals.Comment: 26 pages, 5 figure
- …