8,761 research outputs found
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.
Persistent spin current in spin-orbit coupling systems in the absence of an external magnetic field
The spin-orbit coupling systems with a zero magnetic field is studied under
the equilibrium situation, {\it i.e.}, without a voltage bias. A persistent
spin current is predicted to exist under most circumstances, although the
persistent charge current and the spin accumulation are identically zero. In
particular, a two-dimensional quantum wire is investigated in detail.
Surprisingly, a persistent spin current is found to flow along the confined
direction, due to the spin precession in accompany with the particle motion.
This provides an interesting example of constant spin flowing without inducing
a spin accumulation, contrary to common intuition.Comment: 4 pages, 5 figure
Superconductivity of the Ternary Boride Li_2Pd_3B Probed by ^{11}B NMR
We report a ^{11}B NMR measurement on the recently discovered superconductor
Li_2Pd_3B. The nuclear spin lattice relaxation rate 1/T_1 shows a well-defined
coherence peak just below T_c (H=1.46 T)=5.7 K, and the spin susceptibility
measured by the Knight shift also decreases below T_c. These results indicate
that the superconductivity is of conventional nature, with an isotropic gap.
Our results also suggest that the -electrons of boron and the d-electrons of
palladium that hybridize with boron -electrons are primarily responsible for
the superconductivity.Comment: 4 pages, 5 figure
Bias-controllable intrinsic spin polarization in a quantum dot
We propose a novel scheme to efficiently polarize and manipulate the electron
spin in a quantum dot. This scheme is based on the spin-orbit interaction and
it possesses following advantages: (1) The direction and the strength of the
spin polarization is well controllable and manipulatable by simply varying the
bias or the gate voltage. (2) The spin polarization is quite large even with a
weak spin-orbit interaction. (3) Both electron-electron interaction and
multi-energy levels do not weaken but strengthen the spin polarization. (4) It
has the short spin flip time. (5) The device is free of a magnetic field or a
ferromagnetic material. (6) It can be easily realized with present technology.Comment: 9 pages, 5 figure
Photon-assisted electron transport through a three-terminal quantum dot system with nonresonant tunneling channels
We have studied the electron transport through a quantum dot coupled to three
leads in the presence of external microwave fields supplied to different parts
of the considered mesoscopic system. Additionally, we introduced a possible
nonresonant tunneling channels between leads. The quantum dot charge and
currents were determined in terms of the appropriate evolution operator matrix
elements and under the wide band limit the analytical formulas for
time-averaged currents and differential conductance were obtained. We have also
examined the response of the considered system on the rectangular-pulse
modulation imposed on different quantum dot-leads barriers as well as the
time-dependence of currents flowing in response to suddenly removed (or
included) connection of a quantum dot with one of the leads.Comment: 34 pages, 12 figure
The angular spin current and its physical consequences
We find that in order to completely describe the spin transport, apart from
spin current (or linear spin current), one has to introduce the angular spin
current. The two spin currents respectively describe the translational and
rotational motion of a spin. The definitions of these spin current densities
are given and their physical properties are discussed. Both spin current
densities appear naturally in the spin continuity equation. Moreover we predict
that the angular spin current can also induce an electric field , and
in particular scales as at large distance , whereas the
field generated from the linear spin current goes as .Comment: 7 pages, 2 figure
Deficits in burrowing behaviors are associated with mouse models of neuropathic but not inflammatory pain or migraine
Influences of spin accumulation on the intrinsic spin Hall effect in two dimensional electron gases with Rashba spin-orbit coupling
In a two dimensional electron gas with Rashba spin-orbit coupling, the
external electric field may cause a spin Hall current in the direction
perpendicular to the electric field. This effect was called the intrinsic spin
Hall effect. In this paper, we investigate the influences of spin accumulation
on this intrinsic spin Hall effect. We show that due to the existence of
boundaries in a real sample, the spin Hall current generated by the intrinsic
spin Hall effect will cause spin accumulation near the edges of the sample, and
in the presence of spin accumulation, the spin Hall conductivity will not have
a universal value. The influences of spin accumulation on the intrinsic spin
Hall effect in narrow strips of two dimensional electron gases with Rashba
spin-orbit coupling are investigated in detail.Comment: 7 pages, 2 figure
- …