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1.
The influence of the Rashba spin-orbit coupling on the electron spin dynamics is investigated for a ballistic semiconductor quantum wire with a finite width. We monitor the spin evolution using the time-dependent Schrödinger equation. The pure spin precession characteristic of the 1D limit is lost in a 2D wire with a finite lateral width. In general, the time evolution in the latter case is characterized by several frequencies and a nonrigid spin motion.Received: 16 April 2003, Published online: 11 August 2003PACS:
73.21.Hb Quantum wires -
73.22.Dj Single particle states 相似文献
2.
Optical spin–flip excitations in the conduction band of III–V semiconductor heterostructures are considered theoretically taking into account structure inversion asymmetry (SIA) and bulk inversion asymmetry (BIA) of such systems. Possible spin transitions both in the absence of a magnetic field (B=0) as well as in the presence of a magnetic field B parallel to the growth direction [0 0 1] are investigated. The theory is based on the three-level model of the narrow-gap band structure including the BIA [Phys. Rev. 100 (1955) 580] and SIA [J. Phys. C. 17 (1984) 6039] contributions. We show in particular that the SIA mechanism not only results in the Bychkov–Rashba spin splitting at B=0 but it also gives rise to the possibility of optical transitions between the two spin-split energy branches. 相似文献
3.
We find proximity-induced spontaneous spin and electric surface currents at all temperatures below the super-conducting T c in an isotropic s-wave superconductor deposited with a thin ferromagnetic metal layer with spin-orbit interaction. The currents are carried by Andreev surface states and generated as a joint effect of the spin-orbit interaction and the exchange field. The background spin current arises in the thin layer due to different local spin polarizations of electrons and holes, which have almost opposite velocities in each of the surface states. The spontaneous surface electric current in the superconductor originates in the asymmetry of Andreev states with respect to sign reversal of the momentum component parallel to the surface. The conditions for electric and spin currents to show up in the system significantly differ from each other. 相似文献
4.
The influence of the Dresselhaus spin-orbit coupling on spin polarization by tunneling through a disordered semiconductor superlattice was investigated. The Dresselhaus spin-orbit coupling causes the spin polarization of the electron due to transmission possibilities difference between spin up and spin down electrons. The electron tunneling through a zinc-blende semiconductor superlattice with InAs and GaAs layers and two variable distance InxGa(1−x)As impurity layers was studied. One hundred percent spin polarization was obtained by optimizing the distance between two impurity layers and impurity percent in disordered layers in the presence of Dresselhaus spin-orbit coupling. In addition, the electron transmission probability through the mentioned superlattice is too much near to one and an efficient spin filtering was recommended. 相似文献
5.
Giant Rashba-like spin-orbit splitting with distinct spin texture in two-dimensional heterostructures
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Jianbao Zhu 《中国物理 B》2021,30(8):87307-087307
Based on first-principles density functional theory calculation, we discover a novel form of spin-orbit (SO) splitting in two-dimensional (2D) heterostructures composed of a single Bi(111) bilayer stacking with a 2D semiconducting In2Se2 or a 2D ferroelectric α-In2Se3 layer. Such SO splitting has a Rashba-like but distinct spin texture in the valence band around the maximum, where the chirality of the spin texture reverses within the upper spin-split branch, in contrast to the conventional Rashba systems where the upper branch and lower branch have opposite chirality solely in the region below the band crossing point. The ferroelectric nature of α-In2Se3 further enables the tuning of the spin texture upon the reversal of the electric polarization with the application of an external electric field. Detailed analysis based on a tight-binding model reveals that such SO splitting texture results from the interplay of complex orbital characters and substrate interaction. This finding enriches the diversity of SO splitting systems and is also expected to promise for spintronic applications. 相似文献
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7.
N. S. Averkiev L. E. Golub G. E. Pikus 《Journal of Experimental and Theoretical Physics》1998,86(4):780-789
A theory of weak localization is constructed for p-type semiconductor structures with a complex Γ8 valence band. An equation for the Cooperon is obtained and solved in the case when spin relaxation cannot be treated as a
perturbation. The anomalous magnetoresistance is calculated in bulk samples as a function of the external deformation and
in quantum wells as a function of the doping level. The results of the theory are represented in a form that allows direct
comparison with experiment.
Zh. éksp. Teor. Fiz. 113, 1429–1445 (April 1998) 相似文献
8.
S. Tarucha D.G. Austing S. Sasaki Y. Tokura W. van der Wiel L.P. Kouwenhoven 《Applied Physics A: Materials Science & Processing》2000,71(4):367-378
The effects of direct Coulomb and exchange interactions on spin states are studied for quantum dots contained in circular
and rectangular mesas. For a circular mesa a spin-triplet favored by these interactions is observed at zero and nonzero magnetic
fields. We tune and measure the relative strengths of these interactions as a function of the number of confined electrons.
We find that electrons tend to have parallel spins when they occupy nearly degenerate single-particle states. We use a magnetic
field to adjust the single-particle state degeneracy, and find that the spin-configurations in an arbitrary magnetic field
are well explained in terms of two-electron singlet and triplet states. For a rectangular mesa we observe no signatures of
the spin-triplet at zero magnetic field. Due to the anisotropy in the lateral confinement single-particle state degeneracy
present in the circular mesa is lifted, and Coulomb interactions become weak. We evaluate the degree of the anisotropy by
measuring the magnetic field dependence of the energy spectrum for the ground and excited states, and find that at zero magnetic
field the spin-singlet is more significantly favored by the lifting of level degeneracy than by the reduction in the Coulomb
interaction. We also find that the spin-triplet is recovered by adjusting the level degeneracy with magnetic field.
Received: 14 April 2000 / Accepted: 17 April 2000 / Published online: 6 September 2000 相似文献
9.
Elementary excitations of a new type in paramagnetic materials with spin-orbit interaction are predicted theoretically within the Rashba model and named the spin remagnetization waves. These normal modes arise from rotation of the spin magnetic moment in a medium where the electric field contains a constant component and a traveling wave component. A method is proposed for exciting these vibrations by illuminating the sample with an oscillating interference pattern. The spin remagnetization waves can be experimentally detected by measuring the dependence of the current through the sample on the oscillation frequency and wave vector of the interference pattern. 相似文献
10.
The tunneling time asymmetry in type II semiconductor heterostructures is related to the phase difference of the reflection coefficients for the two tunneling directions. Analytical expressions and numerical simulations are given for the difference between the left-to-right and right-to-left tunneling times in asymmetric, single and multiple barrier type II heterostructures. 相似文献
11.
In semiconductors with inversion asymmetry, spin-orbit coupling gives rise to the well-known Dresselhaus and Rashba effects. If one considers quantum wells with two or more conduction subbands, an additional, intersubband-induced spin-orbit term appears whose strength is comparable to the Rashba coupling, and which remains finite for symmetric structures. We show that the conduction band spin splitting due to this intersubband spin-orbit coupling term is negligible for typical III-V quantum wells. 相似文献
12.
We formulate a semiclassical theory for systems with spin-orbit interactions. Using spin coherent states, we start from the path integral in an extended phase space, formulate the classical dynamics of the coupled orbital and spin degrees of freedom, and calculate the ingredients of Gutzwiller's trace formula for the density of states. For a two-dimensional quantum dot with a spin-orbit interaction of Rashba type, we obtain satisfactory agreement with fully quantum-mechanical calculations. The mode-conversion problem, which arose in an earlier semiclassical approach, has hereby been overcome. 相似文献
13.
We find a dramatic enhancement of electron propagation along a narrow range of real-space angles from an isotropic source in a two-dimensional quantum well made from a zinc-blende semiconductor. This "electron-beam" formation is caused by the interplay between spin-orbit interaction originating from a perpendicular electric field to the quantum well and the intrinsic spin-orbit field of the zinc-blende crystal lattice in a quantum well, in situations where the two fields are different in strength but of the same order of magnitude. Beam formation is associated with caustics and can be described semiclassically using a stationary phase analysis. 相似文献
14.
The spin polarization phenomenon in lepton circular accelerators had been known for many years.It provides a new approach for physicists to study the spin feature of fundamental particles and the dynamics of spin-orbit coupling,such as spin resonances.We use numerical simulation to study the features of spin under the modulation of orbital motion in an electron storage ring.The various cases of depolarization due to spin-orbit coupling through an emitting photon and misalignment of magnets in the ring are discussed. 相似文献
15.
We investigate the equilibrium property of a mesoscopic ring with a spin-orbit interaction. It is well known that, for a normal mesoscopic ring threaded by a magnetic flux, the electron acquires a Berry phase that induces the persistent (charge) current. Similarly, the spin of an electron acquires a spin Berry phase traversing a ring with a spin-orbit interaction. It is this spin Berry phase that induces a persistent spin current. To demonstrate its existence, we calculate the persistent spin current without an accompanying charge current in the normal region in a hybrid mesoscopic ring. We point out that this persistent spin current describes the real spin motion and can be observed experimentally. 相似文献
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By using the Al'tshuler-Aronov-Spivak (AAS) model, we give the amplitude changing with Rashba spin-orbit interaction (SOI) and Dresselhaus SOI strength. In the first idea 1D square loop (SL), Rashba SOI acts on two sides while Dresselhaus SOI acts on the other two sides. In the second SL, we consume Rashba SOI and Dresselhaus SOI act on four sides simultaneously. This model can be replaced by another one that Rashba SOI and Dresselhaus SOI act on every side independently, and each side is twice long. We theoretically illustrate the influence of the Dresselhaus SOI on node position and number. To explain the “half oscillation” phenomenon found in experiment, we apply Dresselhaus SOI to the ideal 1D SL. The conclusion is that the Dresselhaus SOI has a strong effect on the emergence of “half oscillation”. 相似文献
18.
Using the time-dependent Schrödinger equation, we present the analytical result of the expectation value of spin injected into a two-dimensional electron gas with respect to an arbitrarily spin-polarized electron state and monitor the spin time-evolution. We demonstrate that the expectation value of spin operator Sx is the time-independent, and only the expectation values in the Sy-Sz plane are time-dependent. A detailed study of spin precession in the spin-valve and spin-transistor geometry is presented, in which the initial spin-polarized electron state point perpendicular and parallel to the current direction, respectively. We put forward the possible reason that the resistance change is independent of gate voltage in the spin-valve geometry. Furthermore, it has been shown that the effective magnetic field generated by the spin-orbit interaction is not same with the truly magnetic field. The main effect of the truly magnetic field is to align the spin along the field direction, but the effective magnetic field generated by the spin-orbit interaction does not. 相似文献
19.
Optical pumping experiments onF-centres in potassium halides are described. The ground state polarization of the electronic spins achieved by optical pumping of isolatedF-centres is strongly dependent on the magnetic field and the wave-length of the pumping light. Experimentally it does not show the simple relationship to the magnetic circular dichroism (MCD) that has generally been assumed. A closer theoretical analysis shows indeed that the phenomena depend critically on the kind of spin mixing that prevails in the pumping cycle.If spin orbit coupling in the absorption band is the dominant spin mixing mechanism the sign of the pumping effect will be the same everywhere in the absorption band, if some other mechanism like spin mixing by radiationless transitions or hyperfine coupling to the surrounding nuclear spins prevails, the sign will follow the MCD. In strong magnetic fields experiments argue in favour of the first alternative, in low fields spin mixing by hyperfine coupling becomes important. On this basis the mechanism of optical pumping ofF-centres is discussed, and rate equations are given. 相似文献
20.
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