524 research outputs found
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
Contractor renormalization group theory of the SU() chains and ladders
Contractor renormalization group (CORE) method is applied to the SU()
chain and ladders in this paper. In our designed schemes, we show that these
two classes of systems can return to their original form of Hamiltonian after
CORE transformation. Successive iteration of the transformation leads to a
fixed point so that the ground state energy and the energy gap to the ground
state can be deduced. The result of SU() chain is compared with the one by
Bethe ansatz method. The transformation on spin-1/2 ladders gives a finite gap
in the excited energy spectra to the ground state in an intuitive way. The
application to SU(3) ladders is also discussed.Comment: 4 pages, 4 figures, submitted to Phys. Rev.
Chiral anomaly and anomalous finite-size conductivity in graphene
Graphene is a monolayer of carbon atoms packed into a hexagon lattice to host
two pairs of massless two-dimensional Dirac fermions in the absence of or with
negligible spin-orbit coupling. It is known that the existence of non-zero
electric polarization in reduced momentum space which is associated with a
hidden chiral symmetry will lead to the zero-energy flat band of zigzag
nanoribbon. The Adler-Bell-Jackiw chiral anomaly or non-conservation of chiral
charges at different valleys can be realized in a confined ribbon of finite
width. In the laterally diffusive regime, the finite-size correction to
conductivity is always positive and goes inversely with the square of the
lateral dimension W, which is different from the finite-size correction
inversely with W from boundary modes. This anomalous finite-size conductivity
reveals the signature of the chiral anomaly in graphene, and is measurable
experimentally.Comment: 5 pages, 2 figure
Controllable quantum spin precession by Aharonov-Casher phase in conducting ring
We investigate quantum spin transport in a structure of conducting ring,
embedded in textured electric field, with two leads, and obtain an exact
solution for the problem. The spin precession induced by the Aharonov-Casher
phase is studied. It is shown that the spin-polarized current and its
polarizability can be controlled by the electric field. As a result the
polarizability is a function of the geometric phase which originates from the
spin-orbital interaction in the ring.
72.25.-b, 03.65.VfComment: 10 pages, 4 figure
Complete phase diagram and topological properties of interacting bosons in one-dimensional superlattices
The interacting bosons in one-dimensional inversion-symmetric superlattices
are investigated from the topological aspect. The complete phase diagram is
obtained by an atomic-limit analysis and quantum Monte Carlo simulations and
comprises three kinds of phases: superfluid, persisted charge-density-wave and
Mott insulators, and emergent insulators in the presence of nearest-neighbor
hoppings. We find that all emergent insulators are topological, which are
characterized by the Berry phase and a pair of degenerate in-gap boundary
states. The mechanism of the topological bosonic insulators is qualitatively
discussed and the ones with higher fillings can be understood as a
-filling topological phase on a background of trivial
charge-density-wave or Mott insulators.Comment: 6 pages, 8 figures. Accelpted for publication in Phys. Rev.
Spin-Current-Induced Charge Accumulation and Electric Current in Semiconductor Nanostructures with Rashba Spin-Orbit Coupling
We demonstrate that the flow of a longitudinal spin current with different
spin polarization will induce different patterns of charge accumulation in a
two-terminal strip, or electric current distribution in a four-terminal
Hall-bar structure, of two-dimensional electron gas with Rashba spin-orbit
coupling (RSOC). For an in-plane polarized spin current, charges will
accumulate either by the two lateral edges or around the center of the strip
structure while, for an out-of-plain polarized spin current, charge densities
will show opposite signs by the two lateral edges leading to a Hall voltage.
Our calculation offers a new route to experimentally detect or differentiate
pure spin currents with various spin polarization.Comment: 4 pages, 3 figure
Spin and orbital valence bond solids in a one-dimensional spin-orbital system: Schwinger boson mean field theory
A generalized one-dimensional spin-orbital model is
studied by Schwinger boson mean-field theory (SBMFT). We explore mainly the
dimer phases and clarify how to capture properly the low temperature properties
of such a system by SBMFT. The phase diagrams are exemplified. The three dimer
phases, orbital valence bond solid (OVB) state, spin valence bond solid (SVB)
state and spin-orbital valence bond solid (SOVB) state, are found to be favored
in respectively proper parameter regions, and they can be characterized by the
static spin and pseudospin susceptibilities calculated in SBMFT scheme. The
result reveals that the spin-orbit coupling of type serves
as both the spin-Peierls and orbital-Peierles mechanisms that responsible for
the spin-singlet and orbital-singlet formations respectively.Comment: 6 pages, 3 figure
Topological Anderson Insulator
Disorder plays an important role in two dimensions, and is responsible for
striking phenomena such as metal insulator transition and the integral and
fractional quantum Hall effects. In this paper, we investigate the role of
disorder in the context of the recently discovered topological insulator, which
possesses a pair of helical edge states with opposing spins moving in opposite
directions and exhibits the phenomenon of quantum spin Hall effect. We predict
an unexpected and nontrivial quantum phase termed "topological Anderson
insulator," which is obtained by introducing impurities in a two-dimensional
metal; here disorder not only causes metal insulator transition, as
anticipated, but is fundamentally responsible for creating extended edge
states. We determine the phase diagram of the topological Anderson insulator
and outline its experimental consequences.Comment: 4 pages, 4 figure
Transverse electric current induced by optically injected spin current in cross-shaped InGaAs/InAlAs system
We examine electric response of a linearly polarized light normally shed on a
cross-shaped quasi 2-dimensional InGaAs/InAlAs system with structure inversion
asymmetry. The photo-excited conduction electrons carry a pure spin current
with in-plane spin polarization due to the Rashba spin-orbit interaction. We
use Landauer-B\"{u}ttiker formalism to show that this spin current induces two
inward or outward transverse charge currents, which are observable in
experiments. This effect may serve as an experimental probe of certain types of
spin current.Comment: 5 pages, 3 figure
The SU(3) bosons and the spin nematic state on the spin-1 bilinear-biquadratic triangular lattice
A bond-operator mean-field theory in the SU(3) bosons representation is
developed to describe the antiferro-nematic phase of the spin-1
bilinear-biquadratic model. The calculated static structure factors reveal
delicately that the antiferro-nematic state may exhibit both the ferro- and
antiferro-quadruple long-range orders, which is reminiscent of the ferrimagnets
or the canted antiferromagnets. This result may influence the spin wave theory
concerned with this phase. Possible relevance of this unconventional state to
the quasi-two-dimensional triangular material NiGa2S4 is addressed.Comment: 8pages, 6figure
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