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1.
We study the scattering of an electron of a 2DEG through a large point contact separating a region where the electrons are free and a region where the Rashba spin-orbit coupling is present. The scattering depends dramatically on the electron incidence angle showing double refraction within the Rashba region. For incidence not normal to the interface the electron spin state is not conserved. The calculated conductance exhibits an oscillating behavior as a function of spin state of the incident electrons with different spin down and spin up currents. Our model describes both a ferromagnetic semimetallic source and a simple metallic injection electrode. In the first case the electrons are injected in a pure spin state and in the second one they are unpolarized, that is in a statistical mixture of spin up and down states. In both the cases the passage through the large point contact produces spin polarized currents.Received: 30 July 2003, Published online: 23 December 2003PACS:
85.75.Hh Spin polarized field effect transistors - 72.25.-b Spin polarized transport - 73.23.Ad Ballistic transport 相似文献
2.
H.-C. Wu J. Meyer-ter-Vehn 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(2):443-449
The coherent reflectivity of a dense, relativistic,
ultra-thin electron layer is derived analytically for an obliquely
incident probe beam. Results are obtained by two-fold Lorentz
transformation. For the analytical treatment, a plane uniform
electron layer is considered. All electrons move with uniform
velocity under an angle to the normal direction of the plane; such
electron motion corresponds to laser acceleration by direct action
of the laser fields, as it is described in a companion paper [Eur. Phys. J. D 55, 433 (2009)]. Electron density is chosen high enough to ensure that many
electrons reside in a volume λR
3, where λR is the
wavelength of the reflected light in the rest frame of the layer.
Under these conditions, the probe light is back-scattered coherently
and is directed close to the layer normal rather than the direction
of electron velocity. An important consequence is that the Doppler
shift is governed by γx=(1-(Vx/c)2)-1/2 derived from
the electron velocity component Vx in normal direction rather
than the full γ-factor of the layer electrons. 相似文献
3.
We investigate spin-dependent electron transport through graphene-based Rash ba-strain double junctions. It is found that when electrons are injected from left normal graphene region, high spin polarization oscillation is achieved due to the wave-vector-dependent resonant tunneling. The spin polarization is negligible once the incident direction is reversed. Such a remarkable difference arises from pseudogap caused by the Rashba spin-orbit interaction. 相似文献
4.
Defining a spin connection is necessary for formulating Dirac's bispinor equation in a curved space-time. Hestenes has shown
that a bispinor field is equivalent to an orthonormal tetrad of vector fields together with a complex scalar field. In this
paper, we show that using Hestenes' tetrad for the spin connection in a Riemannian space-time leads to a Yang-Mills formulation
of the Dirac Lagrangian in which the bispinor field Ψ is mapped to a set of SL(2,R)× U(1) gauge potentials FαK and a complex scalar field ρ. This result was previously proved for a Minkowski space-time using Fierz identities. As an
application we derive several different non-Riemannian spin connections found in the literature directly from an arbitrary
linear connection acting on the tensor fields (FαK, ρ). We also derive spin connections for which Dirac's bispinor equation is form invariant. Previous work has not considered
form invariance of the Dirac equation as a criterion for defining a general spin connection. 相似文献
5.
L. G. Moyano A. P. Majtey C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):493-500
We introduce, and numerically study, a system of N symplectically and globally coupled
standard maps localized in a d=1 lattice array. The global coupling is modulated
through a factor r-α, being
r the distance between maps. Thus, interactions are long-range (nonintegrable) when
0≤α≤1, and short-range (integrable) when α>1.
We verify that the largest Lyapunov exponent λM scales as λM ∝
N-κ(α), where κ(α) is positive when interactions are
long-range, yielding weak chaos in the thermodynamic
limit N↦∞ (hence λM→0). In the short-range case,
κ(α) appears to vanish,
and the behaviour corresponds to strong chaos. We show that, for certain
values of the control parameters of the system, long-lasting metastable states
can be present. Their duration tc scales as tc ∝Nβ(α),
where β(α) appears to be numerically in agreement with the following
behavior: β>0 for 0 ≤α< 1, and zero for α≥1.
These results are consistent with features typically found in nonextensive statistical mechanics.
Moreover, they exhibit strong similarity between the present
discrete-time system, and the α-XY Hamiltonian ferromagnetic model. 相似文献
6.
O.L. Safronov 《Communications in Mathematical Physics》1998,193(1):233-243
Given two selfadjoint operators A and V=V
+ -V
-, we study the motion of the eigenvalues of the operator A(t)=A-tV as t increases. Let α>0 and let λ be a regular point for A. We consider the quantities N
+(λ,α), N
-(λ,α), N
0(λ,α) defined as the number of the eigenvalues of the operator A(t) that pass point λ from the right to the left, from the left to the right or change the direction of their motion exactly
at point λ, respectively, as t increases from 0 to α>0. An abstract theorem on the asymptotics for these quantities is presented. Applications to Schr?dinger
operators and its generalizations are given.
Received: 9 April 1997 / Accepted: 26 August 1997 相似文献
7.
R. B. Morgunov 《JETP Letters》2010,92(3):156-160
A photocontrolled resonance decrease in microhardness, which is due to the application of mutually perpendicular static and
microwave fields, in γ-irradiated KCl:Fe crystals has been revealed. It has been found that the magnetic plasticity of unirradiated
γ-KCl:Fe crystals is due to the resonance effect of magnetic fields on two types of impurity centers: first, centers containing
Fe2+-ν
c
ion-vacancy pairs and, second, centers containing Fe+ ions. The illumination of γ-KCl:Fe crystals with F-light (with a wavelength of λ = 500–600 nm) is accompanied by rearrangement of the spectrum of electron paramagnetic resonance
detected by a change in microhardness. The effect of F-light on the spectrum of magnetic resonance plasticity is manifested as the suppression of the spectra of Fe2+-ν
c
ions with effective g-factors of 7.0 and 3.5 due to their recombination with F-electrons and reconstruction to Fe+ centers with g-factors of 2.2 and 4.1. 相似文献
8.
We solve the general problem of mixing of electromagnetic and scalar or pseudoscalar fields coupled by axion-type interactions
L
int = g
ϕ
ϕε
μναβ
F
μν
F
αβ
. The problem depends on several dimensionful scales, including the magnitude and direction of background magnetic field,
the pseudoscalar mass, plasma frequency, propagation frequency, wave number, and finally the pseudoscalar coupling. We apply
the results to the first consistent calculations of the mixing of light propagating in a background magnetic field of varying
directions, which show a great variety of fascinating resonant and polarization effects.
相似文献
9.
New experimental data on the binding energyB
λλ
ofλλ6He, reported very recently, come up with the valuesB
λλ
= 725 ±0.14 MeV and ΔBλλ = 101 ±0.2 MeV which are substantially lower than the old dataB
λλ
= 109 ±0.8 MeV and ΔBλλ = 4.7±10 MeV in use in literature since 1966. In view of the new data we decided to undertake a re-study of the
λλ
6
He hypernucleus using the same three-body model (α-λ-λ) with a simple coordinate space variational approach which was employed
earlier with the old data onλλ/6He. After fitting different λ-λ potentials to the new data of
λλ
6
He we have applied our method to study some double-λ hypernuclei in light, medium and heavy mass regions and have determined
the structural quantities like Bλλ, the r.m.s. values of core-λ (〈rcore-λ〉〉) and λ-λ (〈rλ-λ〉〉) distances theoretically. The core-λ interaction considered is of Woods-Saxon type. The strength and the range of the core-A
potential have been adjusted to reproduce the λ-binding energy(B
λ)
. These are in good agreement with the relativistic mean field (RMF) results. Our study shows that the λ-λ bonding energy
ΔBλλ decreases with increasing mass number from
λλ
10
Be to
λλ
210
Pb of a double-A hypernucleus 相似文献
10.
A variational approach is developed for bound state calculations in three- and four-electron atomic systems. This approach
can be applied to determine, in principle, an arbitrary bound state in three- and four-electron ions and atoms. Our variational
wave functions are constructed from four- and five-body Gaussoids that respectively depend on six (r
12, r
13, r
14, r
23, r
24, r
34) and ten (r
12, r
13, r
14, r
15, r
23, r
24, r
25, r
34, r
35 and r
45) relative coordinates. The approach allows operating with the more than one electron spin functions. In particular, the trial
wave functions for the 1
S states in four-electron atomic systems include the two independent spin functions χ1 = αβαβ + βαβα − βααβ − αββα and χ2 = 2ααββ + 2ββαα − βααβ − αββα − βαβα − αβαβ. We also discuss the construction of variational wave functions for the excited
23
S states in four- electron atomic systems. 相似文献
11.
V. Ya. Demikhovskii G. M. Maksimova E. V. Frolova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(5):678-685
Dynamics of electron wave packets in an asymmetric quantum well in the presence of Rashba spinorbit coupling was analytically
and numerically studied. Electron Green’s functions were introduced and the evolution of 1D and 2D wave packets was studied. The effect of packet splitting caused by the presence of two branches with different chiralities
in the Rashba Hamiltonian spectrum and zitterbewegung, i.e., packet center’s jitter, was studied. Spatial components of the
spin density were calculated. It was shown that the component of the spin density S
y
in split parts of the wave packet has opposite signs, and two other spin density components oscillate in space between scattering
packets. 相似文献
12.
We consider the families of entire transcendental maps given by F
λ,m
(z) = λz
m
exp(z), where m ≥ 2. All functions F
λ,m
have a superattracting fixed point at z = 0, and a critical point at z = −m. In the parameter planes we focus on the capture zones, i.e., λ values for which the critical point belongs to the basin
of attraction of z = 0, denoted by A(0). In particular, we study the main capture zone (parameter values for which the critical point lies in the immediate basin,
A
*(0)) and prove that is bounded, connected and simply connected. All other capture zones are unbounded and simply connected.
For each parameter λ in the main capture zone, A(0) consists of a single connected component with non-locally connected boundary. For all remaining values of λ, A
*(0) is a quasidisk. On a different approach, we introduce some families of holomorphic maps of which serve as a model for F
λ,m
, in the sense that they are related by means of quasiconformal surgery to F
λ,m
.
Both authors were supported by MTM2005-02139/Consolider (including a FEDER contribution) and CIRIT 2005 SGR01028. The first
author was also supported by MTM2006-05849/Consolider (including a FEDER contribution). 相似文献
13.
Pedro Freitas 《Communications in Mathematical Physics》2001,217(2):375-382
We consider the problem of minimizing the eigenvalues of the Schr?dinger operator H=−Δ+αF(κ) (α>0) on a compact n-manifold subject to the restriction that κ has a given fixed average κ0.
In the one-dimensional case our results imply in particular that for F(κ)=κ2 the constant potential fails to minimize the principal eigenvalue for α>αc=μ1/(4κ0
2), where μ1 is the first nonzero eigenvalue of −Δ. This complements a result by Exner, Harrell and Loss, showing that the critical value
where the constant potential stops being a minimizer for a class of Schr?dinger operators penalized by curvature is given
by α
c
. Furthermore, we show that the value of μ1/4 remains the infimum for all α >α
c
. Using these results, we obtain a sharp lower bound for the principal eigenvalue for a general potential.
In higher dimensions we prove a (weak) local version of these results for a general class of potentials F(κ), and then show that globally the infimum for the first and also for higher eigenvalues is actually given by the corresponding
eigenvalues of the Laplace–Beltrami operator and is never attained.
Received: 17 July 2000 / Accepted: 11 October 2000 相似文献
14.
Analysis of THz-wave surface-emitted difference-frequency generation in periodically poled lithium niobate waveguide 总被引:1,自引:0,他引:1
It was shown that the periodically poled LiNbO3-waveguide with period of poling λ≈λ/ng (λ is the wavelength of emitted THz-wave, ng is a refractive index corresponding to optical group velocity) emits THz-wave difference-frequency generation (DFG) in the
direction normal to the surface of the planar waveguide. The 5% distinction between the manufactured and required periods
of gratings results only in a small deflection (∼6°) of the output THz-beam from the normal direction. The dependence of DFG
efficiency on mode size is analyzed. The output THz power at λ=150 μm is estimated as 2 mW, taking into account imperfections
in coupling incident beams with guided modes. It was shown that the efficiency of THz-wave DFG in surface-emitting geometry
is more than for collinear geometry in bulk crystal, especially in the high-absorption wavelength region.
Received: 16 May 2001 / Revised version: 13 August 2001 / Published online: 2 November 2001 相似文献
15.
Zero field μSR has been used to probe rare earth spin dynamics in the magnetic superconductors, Y1−x
Er
x
Ni2B2C. The muon spin relaxation function is stretched exponential, exp (−(λt)β), in form, as usually found for spin glass systems above the glass temperature. However, the Y1−x
Er
x
Ni2B2C compounds show no evidence of coexisting superconducting and static spin glass ground states even at concentrations below
the critical value (x=0.6) for long range antiferromagnetic order. The temperature dependence of both the muon spin relaxation rate λ and the exponent
β suggests that Er spin dynamics change significantly at the superconducting transition temperature.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
16.
Using the example of an easy-axis antiferromagnet with a magnetic structure of 4
z
−2
x
+
I
− the effect of antisymmetric magnetoelectric interaction on the nature of the refraction of the bulk s- or p-polarized electromagnetic waves, incident from outside at any angle to the surface of the magnet, is studied analytically.
The easy magnetic axis is collinear to the normal to the medium interface. 相似文献
17.
The exponent λ of the structure function F2 ∼x
−λ is calculated using the solution of the DGLAP equation for gluon at lowx reported recently by the present authors. The quantity λ is calculated both as a function ofx at fixedQ
2 and as a function ofQ
2 at fixedx and compared with the most recent data from H1 相似文献
18.
Loktionov E. Yu. Ovchinnikov A. V. Protasov Yu. S. Protasov Yu. Yu. Sitnikov D. S. 《Optics and Spectroscopy》2012,112(4):631-637
The opto-mechanical characteristics, such as the specific mechanical recoil momentum, the specific impulse, and the energy
efficiency, of the laser ablation of flat polymer targets ((C2F4)
n
, (CH2O)
n
) have been determined experimentally for the first time for the case of excitation with femtosecond pulses (τ ∼ 45–70 fs)
of UV-IR (λ ∼ 266, 400, 800 nm) laser radiation (I
0 up to 1015 W/cm2) under normal atmospheric and vacuum (p ∼ 10−4 mbar) conditions. The efficiency of mechanical recoil momentum generation is analyzed for various regimes of the laser irradiation. 相似文献
19.
20.
Let F be a differentiable manifold endowed with an almost K?hler structure (J,ω), α a J-holomorphic action of a compact Lie group on F, and K a closed normal subgroup of which leaves ω invariant.
The purpose of this article is to introduce gauge theoretical invariants for such triples (F,α,K). The invariants are associated with moduli spaces of solutions of a certain vortex type equation on a Riemann surface Σ.
Our main results concern the special case of the triple
where αcan denotes the canonical action of on . We give a complex geometric interpretation of the corresponding moduli spaces of solutions in terms of gauge theoretical
quot spaces, and compute the invariants explicitly in the case r=1.
Proving a comparison theorem for virtual fundamental classes, we show that the full Seiberg–Witten invariants of ruled surfaces,
as defined in [OT2], can be identified with certain gauge theoretical Gromov–Witten invariants of the triple (Hom(ℂ,ℂ<
r
0),αcan, U(1)). We find the following formula for the full Seiberg–Witten invariant of a ruled surface over a Riemann surface of genus
g:
where [F] denotes the class of a fibre. The computation of the invariants in the general case r >1 should lead to a generalized Vafa-Intriligator formula for “twisted”Gromov–Witten invariants associated with sections
in Grassmann bundles.
Received: 22 February 2001 / Accepted: 16 January 2002 相似文献