356 research outputs found
Circulating and persistent currents induced by a current magnification and Aharonov-Casher phase
We considered the circulating current induced by the current magnification
and the persistent current induced by Aharonov-Casher flux. The persistent
currents have directional dependence on the direct current flow, but the
circulating currents have no directional dependence. Hence in the equilibrium,
only the persistent current can survives on the ring. For the charge current,
the persistent charge current cancelled between spin up and down states,
because of the time reversal symmetry of the Hamiltonian on the ring. So there
are only circulating charge currents on the ring for electrons with unpolarized
spin in the nonequilibrium. However, only the persistent spin currents
contributes to the spin currents for electrons with unpolarized spin.Comment: 9 pages and 4 ps figure
Photon-Assisted Quasiparticle Transport and Andreev Transport through an Interacting Quantum Dot
Resonant tunneling through a quantum dot coupled to superconducting
reservoirs in the presence of time-dependent external voltage has been studied.
A general formula of the current is derived based on the nonequilibrium Green's
function technique. Using this formula photon-assisted quasiparticle transport
has been investigated for the quantum dot connected to superconductors. In
addition, resonant Andreev transport through a strongly correlated quantum dot
connected to a normal metallic lead and a superconducting lead is studied.Comment: 9 pages(1 column) with 3 figure
Multi-anyons in the magnetic field
We consider the external magnetic field effects on the two types of anyon
with fractional statistical parameters with coprimes and , one
with fractional charge and flux (type I), the other
with fractional flux and fundamental charge (type II). These
two-types of anyons show different behaviors in the presence of the external
magnetic field. We also considered the geometry in which a two-dimensional
plane contains an island of anyons with different statistical parameter in
their equilibrium. The equilibrium inside an island is shown to be periodic
with respect to the flux through the island. The period for the type I anyon
equals to the integer multiple of the fundamental flux quantum. In the case of
type II anyon the period is found to be the fractional multiple of the
fundamental flux quantum.Comment: revtex, no figure
Ferromagnetic Fixed Point of the Kondo Model in a Luttinger Liquid
The Kondo effect in a Luttinger liquid is studied using the renormalization
group method. By renormalizing the boson fields, scaling equations to the
second order for an arbitrary Luttinger interaction are obtained. For the
ferromagnetic Kondo coupling, a spin bound state(triplet) can be realized
without invoking a nearest neighbor spin interaction in agreement with the
recent Bethe ansatz calculation. The scaling theory in the presence of the
scalar potential shows that there is no interplay between the magnetic and
non-magnetic interaction. Also a study on the crossover behavior of the Kondo
temperature between the exponential and the power law type is presented.Comment: 9 pages, 2 figures. Accepted for publication in J. Phys.: Condens.
Matte
Directional dependence of spin currents induced by Aharonov-Casher phase
We have calculated the persistent spin current of an open ring induced by the
Aharonov-Casher phase. For unpolarized electrons there exist no persistent
charge currents, but persistent spin currents. We show that, in general, the
magnitude of the persistent spin current in a ring depends on the direction of
the direct current flow from one reservoir to another. The persistent spin
current is modulated by the cosine function of the spin precession angle. The
nonadiabatic Aharonov-Casher phase gives anomalous behaviors. The
Aharonov-Anandan phase is determined by the solid angle of spin precession.
When the nonadiabatic Aharonov-Anandan phase approaches a constant value with
the increase of the electric field, the periodic behavior of the spin
persistent current occurs in an adiabatic limit. In this limit the periodic
behavior of the persistent spin current could be understood by the effective
spin-dependent Aharonov-Bohm flux.Comment: 16pages, 5 postscript figures. Submitted to Phys. Rev.
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Controlling the Magnetic Anisotropy of the van der Waals Ferromagnet Fe3GeTe2 through Hole Doping.
Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect. Fe3-xGeTe2 nanoflakes show a significant suppression of the magnetic anisotropy with hole doping. Electronic structure measurements and calculations reveal that the chemical potential shift associated with hole doping is responsible for the reduced magnetic anisotropy by decreasing the energy gain from the spin-orbit induced band splitting. Our findings provide an understanding of the intricate connection between electronic structures and magnetic properties in two-dimensional magnets and propose a method to engineer magnetic properties through doping
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