共查询到20条相似文献,搜索用时 31 毫秒
1.
Hyun-Joo Koo 《Solid State Communications》2009,149(21-22):847-851
The magnetic properties of Ag2V OP2O7 were examined by evaluating its spin exchange interactions in terms of spin dimer analysis based on tight binding calculations and mapping analysis based on first principles density functional theory calculations. Both calculations show that a strong spin exchange interaction occurs through the super-superexchange path J1 with the V…V distance of 5.293 Å. This strong antiferromagnetic interaction forms isolated spin dimer units, which are coupled antiferromagnetically by the spin exchange path J3 to form a two-leg spin ladder that has no spin frustration. The inter–dimer interaction J2 is found to be ferromagnetic, and does not lead to spin frustration. 相似文献
2.
The intrinsic spin Hall effect on spin accumulation and electric conductance in a diffusive regime of a 2D electron gas has been studied for a 2D strip of a finite width. It is shown that the spin polarization near the flanks of the strip, as well as the electric current in the longitudinal direction, exhibit damped oscillations as a function of the width and strength of the Dresselhaus spin-orbit interaction. Cubic terms of this interaction are crucial for spin accumulation near the edges. As expected, no effect on the spin accumulation and electric conductance have been found in case of Rashba spin-orbit interaction. 相似文献
3.
A. Ya. Silenko 《Journal of Experimental and Theoretical Physics》2003,96(4):610-616
Quantum mechanical equations of motion are obtained for particles and spin in media with polarized electrons in the presence of external fields. The motion of electrons and their spins is governed by the exchange interaction, while the motion of positrons and their spin is governed by the annihilation interaction. For particles with spin S ≥ 1, second-order terms in spin are taken into account. The equations obtained can be applied to describe the motion of particles and spin both in magnetic and nonmagnetic media. 相似文献
4.
《Superlattices and Microstructures》2005,37(5):333-336
We derive an expression for the spin current through a tunnel barrier in terms of many-body Green’s functions. The spin current has two possible contributions. One is associated with angular momentum transfer due to spin-polarized charge current crossing the junction. If there are magnetic moments on both sides of the tunnel junction, due to spin accumulation or ferromagnetic ordering, then there is a second contribution related to the exchange coupling between the moments. 相似文献
5.
Peter G. Debrunner 《Hyperfine Interactions》1990,53(1-4):21-35
The phenomenology of a new group of binuclear iron proteins is discussed. The common feature of these proteins is a pair of exchange coupled high spin irons in the diferric, diferrous or ferric-ferrous, trapped valence state. Of particular interest are the cases of intermediate coupling, where the zero-field splittings are comparable to the exchange and possibly the Zeeman interaction. Examples of the Mössbauer analysis of such systems in terms of a spin Hamiltonian are discussed. 相似文献
6.
D. V. Azamat A. Dejneka V. A. Trepakov L. Jastrabik M. Fanciulli V. Y. Ivanov M. Godlewski V. I. Sokolov J. Rosa A. G. Badalyan 《固体物理学:研究快报》2011,5(4):138-140
Electron paramagnetic resonance (EPR) is used to identify the next nearest neighbour Co2+ pairs coupled by spin–spin interaction in Co‐doped ZnO single crystals grown by the hydrothermal technique. These dimer centers are described by a spin Hamiltonian with exchange coupling terms written as interaction between identical effective spins Seff = 1/2 of the lowest ground state Kramers doublets of the two Co2+ ions. The exchange parameters of weakly ferromagnetically coupled next nearest neighbor Co2+ pairs are estimated. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
Relaxation equations are derived for an electron-nuclear spin system, with account of the exchange interaction between electronic spins. It is shown that the relaxation equations can be derived by standard perturbation theory, with the help of the random-local-field method, based on a certain stochastic model of the exchange coupling. The perturbation theory is carried out to second order only for the interactions which are directly responsible for the relaxation, and the exchange interaction can be arbitrarily strong. The relaxation times are expressed in terms of the spectral densities of the correlation functions, which describe not only the thermal broadening of the electron-nuclear interactions, but also the exchange interaction. An explicit expression is obtained for these correlation functions. 相似文献
8.
Hai-Zhou Lu Rong Lü Shun-Qing Shen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(1):69-75
Dynamics of two quantum dots coupled to electrodes with spin bias is
investigated theoretically by means of the master equations. The two dots are coupled via exchange interaction. When the
exchange interaction is much smaller than the lead-dot 2 coupling and dot 2 is under a symmetric spin bias,
an initially fully polarized electron spin in dot 1 undergoes an oscillation with ignorable
attenuation. Meanwhile, the direction of charge current flowing through dot 2 oscillates in
the same period as that of the spin in dot 1. This allows to reverse or nearly noninvasively read
out the spin in dot 1, by switching on and off the exchange
interaction for a duration of half-integer or integer periods of the
oscillation, respectively. 相似文献
9.
通过分析不同温度下HgMnTe磁性二维电子气Shubnikov-de Hass(SdH)振荡的拍频现象,研究了量子阱中电子自旋 轨道相互作用和spd交换相互作用.结果表明:(1)在零磁场下,电子的自旋 轨道相互作用导致电子发生零场自旋分裂;(2)在弱磁场下,电子的自旋-轨道相互作用占主导地位,并受Landau分裂和Zeeman分裂的影响,电子的自旋分裂随磁场增加而减小;(3)在高磁场下,电子的spd交换相互作用达到饱和,电子的自旋分裂主要表现为Zeeman分裂.实验证明了当电子的Zeeman分裂能量与零场
关键词:
磁性二维电子气
Zeeman分裂
Rashba自旋分裂 相似文献
10.
P. Liu S.-J. Xiong 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):513-516
The spin Hall transport properties in a two-dimensional electron
system with both Rashba spin-orbit coupling (SOC) and magnetic
impurities are investigated. Electrons are scattered by impurities
through an exchange interaction that leads to spin flip-flop
processes and so changes the spin Hall effect induced by the SOC.
The spin Hall conductance is calculated in a 4-terminal system
using the Landauer-Buttiker formula and Green function approach.
In comparison with the simulation results on nonmagnetic
impurities doping systems, our results reveal that the spin Hall
conductance is still nonzero in a system with a large density of
magnetic impurities and a finite intensity of the exchange
interaction between the electrons and impurities, and its sign may
be altered when the doping density and interaction strength are
large enough. 相似文献
11.
Nedko B. Ivanov Jörg Ummethum Jürgen Schnack 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(10):1-13
For the time being isotropic three-body exchange interactions are scarcely explored and mostly used as a tool for constructing various exactly solvable one-dimensional models, although, generally speaking, such competing terms in generic Heisenberg spin systems can be expected to support specific quantum effects and phases. The Heisenberg chain constructed from alternating S = 1 and σ = 1/2 site spins defines a realistic prototype model admitting extra three-body exchange terms. Based on numerical density-matrix renormalization group (DMRG) and exact diagonalization (ED) calculations, we demonstrate that the additional isotropic three-body terms stabilize a variety of partially-polarized states as well as two specific non-magnetic states including a critical spin-liquid phase controlled by two Gaussinal conformal theories as well as a critical nematic-like phase characterized by dominant quadrupolar S-spin fluctuations. Most of the established effects are related to some specific features of the three-body interaction such as the promotion of local collinear spin configurations and the enhanced tendency towards nearest-neighbor clustering of the spins. It may be expected that most of the predicted effects of the isotropic three-body interaction persist in higher space dimensions. 相似文献
12.
We find the emergence of strong correlations and universality on the approach to the quantum critical points of a two-impurity Anderson model. The two impurities are coupled by an interimpurity exchange interaction J and direct interaction U{12} and are hybridized with separate conduction channels. The low energy behavior is described in terms of renormalized parameters. We show that on the approach to the transitions to a local singlet and a local charged ordered state, the quasiparticle weight factor z→0, and the renormalized parameters can be expressed in terms of a single energy scale T{*}. The values of the renormalized interaction parameters in terms of T{*} can be predicted from the condition of continuity of the spin and charge susceptibilities, and correspond to strong correlation. These predictions are confirmed by the numerical renormalization group calculations, including the case when the on site interaction U=0. 相似文献
13.
Dyakonov MI 《Physical review letters》2007,99(12):126601
Because of spin-orbit interaction, an electrical current is accompanied by a spin current resulting in spin accumulation near the sample edges. Due again to spin-orbit interaction this causes a small decrease of the sample resistance. An applied magnetic field will destroy the edge spin polarization leading to a positive magnetoresistance. This effect provides means to study spin accumulation by electrical measurements. The origin and the general properties of the phenomenological equations describing coupling between charge and spin currents are also discussed. 相似文献
14.
We theoretically investigate the spin accumulation in two parallel coupled quantum dots (QDs) with ferromagnetic and superconducting electrodes. Due to the ferromagnetic lead, the spin accumulation appears on the resonance of Andreev reflection. The spin accumulation in each of the two QDs can be controlled by the gate voltage. The sign of the spin accumulation is also controllable by tuning the bias. Furthermore, tuning the magnetic flux can exchange the amplitude of the spin accumulation in the two QDs. The Aharonov-Bohm oscillation effects also provides a way to control the spin accumulation of each QD. 相似文献
15.
The multielectron theory of exchange interactions taking into account both electrostatic interactions between electrons (“potential” exchange) and electron transfer between magnetic centers (“kinetic” exchange) has been developed on the basis of Bogolubov's procedure using double irreducible operators. The final hamiltonian contains a number of isotropic and anisotropic terms. The exchange interaction parameter variations with the distance have been calculated. The terms determining the dependence on the occupancy of magnetic shells are shown to be of the same order of magnitude as the “potential” exchange and two orders of magnitude less than the “kinetic” exchange. It is shown that in the model adopted the mechanisms of direct exchange interactions always favour the antiferromagnetic spin ordering 相似文献
16.
Dibaryon quark-exchange kernels are constructed in explicit analytic form for the tensor and spin-orbit terms of the one-gluon-exchange quark-quark Breit interaction and for spin-orbit terms generated by quark-confinement mechanisms. The spin operators needed are defined through their spin-reduced matrix elements including those needed for interactions coupling NN, NΔ, and ΔΔ channels. Effective baryon-baryon spin-orbit potentials, generated through the Wigner transforms of the quark-exchange kernels with the use of a local momentum approximation, show that the NN spin-orbit interaction derived from the symmetric spin-orbit term of the one-gluon-exchange quark-quark interaction is in general agreement with the short-range part of phenomenological potentials derived from NN scattering. With the inclusion of the antisymmetric spin-orbit one-gluon-exchange terms and spin-orbit terms generated by confining potentials the full triplet-odd NN spin-orbit potential is greatly reduced in the 0.5–1 fm range. The uncertainties associated with spin-orbit terms generated by quark-confinement mechanisms are emphasized. The relative importance of various possible quark-gluon exchange terms is studied and shows that models which neglect some types of exchange terms are open to question. An SU(3)-flavor symmetric model for N-hyperon spin-orbit potentials leads to an NΛ spin-orbit potential only slightly weaker than the NN spin-orbit potential. 相似文献
17.
18.
We study an anisotropic spin cluster of 3 spin S=1/2 particles with antiferromagnetic exchange interaction with non-uniform coupling constants. A time-dependent magnetic field is applied to control the time evolution of the cluster. It is well known that for an odd number og sites a spin cluster qubit can be defined in terms of the ground state doublet. The universal one-qubit logic gate can be constructed from the time evolution operator of the non-autonomous many-body system, and the six basic one-qubit gates can be realized by adjusting the applied time-dependent magnetic field. 相似文献
19.
We study an anisotropic spin cluster of 3 spin S=1/2 particles with antiferromagnetic exchange interaction with non-uniform coupling constants. A time-dependent magnetic field is
applied to control the time evolution of the cluster. It is well known that for an odd number of sites a spin cluster qubit can be defined in terms of the ground state doublet. The universal one-qubit logic gate can be constructed from the time evolution
operator of the non-autonomous many-body system, and the six basic
one-qubit gates can be realized by adjusting the applied
time-dependent magnetic field. 相似文献
20.
We investigate the scanning tunneling spectroscopy (STS) of a two-orbital Anderson impurity
adsorbed on a metallic surface by using the numerical renormalization group (NRG) method. The density
of state of magnetic impurity and the local conduction electron are calculated. We obtain the Fano
resonance line shape in the STM conductance at zero temperature. For the impurity atom with
antiferromagnetic inter-orbital exchange interaction and a spin singlet ground state, we show that a
dip in the STM spectra around zero bias voltage regime and side peaks of spin excitation can be
observed. The spin excitation energy is proportional to the exchange interaction strength. As the
exchange interaction is ferromagnetic, the underscreened Kondo effect dominates the low energy
properties of this system, and it gives rise to drastically different STM spectra as compared with the
spin singlet case. 相似文献