3,593 research outputs found
Light Induced Hall effect in semiconductors with spin-orbit coupling
We show that optically excited electrons by a circularly polarized light in a
semiconductor with spin-orbit coupling subject to a weak electric field will
carry a Hall current transverse to the electric field. This light induced Hall
effect is a result of quantum interference of the light and the electric field,
and can be viewed as a physical consequence of the spin current induced by the
electric field. The light induced Hall conductance is calculated for the p-type
GaAs bulk material, and the n-type and p-type quantum well structures.Comment: 5 pages, 3 figure
On the origin of biquadratic exchange in spin 1 chains
One dimensional spin 1 systems may have a rich phase diagram including
Haldane gap and dimerized phases if the usually very small biquadratic exchange
becomes significant. We show that this unlikely condition may be fulfilled in
electron systems with quasi-degenerate orbitals. This mechanism may have been
experimentally realized in the spin 1 chain LiVGeO. The implications
for the exploration of the physics and quantum chemistry of spin 1 chains are
discussed.Comment: 4 pages, 4 Postscript figures. To appear in Eur. Phys. J B as a Rapid
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Vortex Structures in Model p-Wave Superconducting Sr2RuO4 -- Single 2-Dimensional Band v.s. Quasi-1-Dimensional Band
There have been an interesting debate on the primary source of chiral p-wave
superconductivity in Sr2RuO4. We present a comparative study on the vortex
structure between a single 2-dimensional (2D) band and quasi-1D band model by
using Bogoliubov-de Gennes theory. The pattern of the iso-values of the local
density of state around a vortex has a diamond shape in the quasi-1D model and
is much more isotropic in the 2D model. The spin lattice relaxation rate well
below the superconducting transition temperature is greatly enhanced in the
vortex state in the 2D model but not in the quasi-1D model. These features can
be tested by using scanning tunneling microscope and NMR to distinguish the
models for the superconductivity in Sr2RuO4.Comment: 7 pages, 6 fig
Theory for superconductivity in alkali chromium arsenides A2Cr3As3 (A=K,Rb,Cs)
We propose an extended Hubbard model with three molecular orbitals on a
hexagonal lattice with symmetry to study recently discovered
superconductivity in ACrAs (A=K,Rb,Cs). Effective pairing
interactions from paramagnon fluctuations are derived within the random phase
approximation, and are found to be most attractive in spin triplet channels. At
small Hubbard and moderate Hund's coupling, the pairing arises from
3-dimensional (3D) band and has a spatial symmetry
, which gives line nodes in the gap function. At large
, a fully gapped -wave state, dominates at the quasi-1D
-band
Symmetry of superconducting states with two orbitals on a tetragonal lattice: application to
We use group theory to classify the superconducting states of systems with
two orbitals on a tetragonal lattice. The orbital part of the superconducting
gap function can be either symmetric or anti-symmetric. For the orbital
symmetric state, the parity is even for spin singlet and odd for spin triplet;
for the orbital anti-symmetric state, the parity is odd for spin singlet and
even for spin triplet. The gap basis functions are obtained with the use of the
group chain scheme by taking into account the spin-orbit coupling. In the weak
pairing limit, the orbital anti-symmetric state is only stable for the
degenerate orbitals. Possible application to iron-based superconductivity is
discussed.Comment: published versio
Electronic structure near an impurity and terrace on the surface of a 3-dimensional topological insulator
Motivated by recent scanning tunneling microscopy experiments on surfaces of
BiSb\cite{yazdanistm,gomesstm} and
BiTe,\cite{kaptunikstm,xuestm} we theoretically study the electronic
structure of a 3-dimensional (3D) topological insulator in the presence of a
local impurity or a domain wall on its surface using a 3D lattice model. While
the local density of states (LDOS) oscillates significantly in space at
energies above the bulk gap, the oscillation due to the in-gap surface Dirac
fermions are very weak. The extracted modulation wave number as a function of
energy satisfies the Dirac dispersion for in-gap energies and follows the
border of the bulk continuum above the bulk gap. We have also examined
analytically the effects of the defects by using a pure Dirac fermion model for
the surface states and found that the LDOS decays asymptotically faster at
least by a factor of 1/r than that in normal metals, consistent with the
results obtained from our lattice model.Comment: 7 pages, 5 figure
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