共查询到20条相似文献,搜索用时 500 毫秒
1.
The superconducting state can be influenced by injecting spin-polarized current in a controlled manner by properly tailoring the interfacial transmittivity between a ferromagnet (F) and a superconductor (S), resulting in a large magnetoresistance of over 1100% for a F/I/S/I/F multilayer system (I insulator). Because of the competition between ferromagnetism and superconductivity, the superconducting transition temperature (T(C)) in the spin-parallel configuration is shifted below that in the spin antiparallel configuration. The T(C) shift is attributed to ferromagnet-induced nonequilibrium spin carriers in the superconductors. 相似文献
2.
We report nonlocal spin injection and detection experiments on mesoscopic Co-Al2O3-Cu spin valves. We have observed a temperature-dependent asymmetry in the nonlocal resistance between parallel and antiparallel configurations of the magnetic injector and detector. This strongly supports the existence of a nonequilibrium resistance that depends on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal providing evidence for increasing interface spin scattering with temperature. 相似文献
3.
《Physica E: Low-dimensional Systems and Nanostructures》2009,41(10):3037-3041
The spin current driven by an alternating field in a magnetic-oscillating quantum dot system coupled to single metal electrode is investigated. The Keldysh's nonequilibrium Green function technique is used to find the general formulas of the time-averaged spin current and its differential. We find that for a given rotating frequency, the spin current increases rapidly and shows a series of steps with increasing driven frequency. As the driven frequency is further increasing, the spin current can be significantly enhanced and approaches a stable value. The influence of the gate voltage and temperature on the spin current is examined in detail. 相似文献
4.
《Current Applied Physics》2019,19(12):1362-1366
Based on a spin drift-diffusion model, we theoretically investigate the spin-orbit torque in ferromagnet/normal metal/insulator trilayers with considering the Rashba interfacial spin-orbit coupling at the normal metal/insulator interface. We find that the spin-orbit torque shows the opposite normal-metal-thickness dependences for the bulk spin-orbit coupling effect in the normal metal layer and for the interfacial spin-orbit coupling effect at the normal metal/insulator interface, offering a way to disentangle these two spin-orbit coupling effects. Moreover, we show that the conventional interpretation based on the bulk spin-orbit coupling effect overestimates the spin Hall angle and underestimates the spin diffusion length of the normal metal layer, when the interfacial contribution is non-negligible. Our result, a concise analytic expression of the spin-orbit torque considering both bulk and interface spin-orbit coupling effects, will be useful to design and interpret experiments on spin-orbit torque experiments in ferromagnet/normal metal/insulator trilayers. 相似文献
5.
In this paper, spin-dependent transport through a spin diode composed of a quantum dot coupled to a normal metal and a ferromagnetic lead is studied. The current polarization and the spin accumulation are analyzed using the equations of motion method within the nonequilibrium Green’s function formalism. We present a suitable method for computing Green’s function without carrying out any self-consistent calculation. The influence of coupling strength and magnetic field on the spin current is studied and observed that this device cannot work as a spin diode under certain conditions. 相似文献
6.
利用过渡金属掺杂的硅基团簇, 构建了一种自旋分子结; 并利用第一性原理方法, 对其电子自旋极化输运性质进行了研究. 计算表明, 通过过渡金属掺杂可以有效地产生自旋极化电流, 磁性金属Fe和非磁性金属Cr和Mn掺杂的体系呈现出较明显的自旋极化透射现象, 但分子结的自旋极化输运能力与团簇孤立状态下的磁矩无一致性.从Sc到Ni的掺杂, 体系的自旋极化透射能力先增大后迅速减小, 在Fe掺杂的Si12团簇中出现最大值.
关键词:
硅团簇
自旋极化输运
密度泛函理论
非平衡格林函数 相似文献
7.
J.-T. Rebsch 《Physica A》1976,84(1):143-154
A quantum-statistical theory for the nonequilibrium state of a system subjected to a strong external perturbation is derived with the method of the time-dependent generalized canonical statistical operator. Expressions for the response of the nonequilibrium system to a second perturbation are then given. The theory is applied to the problem of double resonance in a system with two different spin species. 相似文献
8.
J. Hooyberghs J. O. Indekeu 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(2):155-163
Nonequilibrium wetting transitions are observed in Monte Carlo simulations of a kinetic spin system in the absence of a detailed
balance condition with respect to an energy functional. A nonthermal model is proposed starting from a two-dimensional Ising
spin lattice at zero temperature with two boundaries subject to opposing surface fields. Local spin excitations are only allowed
by absorbing an energy quantum (photon) below a cutoff energy E
c
. Local spin relaxation takes place by emitting a photon which leaves the lattice. Using Monte Carlo simulation nonequilibrium
critical wetting transitions are observed as well as nonequilibrium first-order wetting phenomena, respectively in the absence
or presence of absorbing states of the spin system. The transitions are identified from the behavior of the probability distribution
of a suitably chosen order parameter that was proven useful for studying wetting in the (thermal) Ising model. 相似文献
9.
The magnetic field of complete spin polarization is calculated in a disorderless single-valley strongly-interacting 2D electron system. In the metallic region above the Wigner-Mott transition, nonequilibrium spin states are predicted, which should give rise to hysteresis in the magnetization. 相似文献
10.
K. Uchida T. Ota K. Harii S. Takahashi S. Maekawa Y. Fujikawa E. Saitoh 《Solid State Communications》2010,150(11-12):524-528
The spin-Seebeck effect (SSE) converts a heat current into a spin current, a flow of spin angular momentum, and spin voltage, the driving force for nonequilibrium spin currents, in a ferromagnetic metal. In this study, the SSE in a ferromagnetic Ni81Fe19 film has been investigated by means of the inverse spin-Hall effect (ISHE) in a Pt film at room temperature. The experimental results measured in the Ni81Fe19/Pt system show that the sign of the thermally induced spin voltage is reversed between the higher- and lower-temperature ends of the Ni81Fe19 film. The ISHE in the Pt film allows us to detect the SSE signal with high sensitivity and to separate it from extrinsic thermoelectric effects. 相似文献
11.
M. M. Glazov 《Journal of Experimental and Theoretical Physics》2016,122(3):472-483
Effects that are related to deviations from thermodynamic equilibrium have a special place in modern physics. Among these, nonequilibrium phenomena in quantum systems attract the highest interest. The experimental technique of spin-noise spectroscopy has became quite widespread, which makes it possible to observe spin fluctuations of charge carriers in semiconductors under both equilibrium and nonequilibrium conditions. This calls for the development of a theory of spin fluctuations of electrons and electron–hole complexes for nonequilibrium conditions. In this paper, we consider a range of physical situations where a deviation from equilibrium becomes pronounced in the spin noise. A general method for the calculation of electron and exciton spin fluctuations in a nonequilibrium state is proposed. A short review of the theoretical and experimental results in this area is given. 相似文献
12.
A. S. Zhuravlev L. V. Kulik V. A. Kuznetsov M. A. Khit’ko I. V. Kukushkin 《JETP Letters》2018,108(6):419-422
The spin polarization features of an electron system and the relaxation of nonequilibrium spin excitations near an even-denominator fractional state of 3/2 in a two-dimensional electron system based on the GaAs/AlGaAs heterostructure are experimentally investigated. It is shown that the 3/2 state is a singular point in the filling factor dependence of the spin ordering of the two-dimensional electron system, at which the spin subsystem is rearranged. A giant slowing down of the relaxation of spin excitations to the ground state is revealed in a certain range of filling factors near filling factor 3/2. 相似文献
13.
Pareek TP 《Physical review letters》2004,92(7):076601
We present a generalized Landauer-Büttiker transport theory for multiterminal spin transport in the presence of spin-orbit interaction. Using this theory we point out that there exists equilibrium spin currents and nonequilibrium pure spin currents, without any magnetic element in the system. Quantitative results are presented for a Y-shaped conductor. It is shown that pure spin currents cause a voltage drop and, hence, can be measured. 相似文献
14.
Detection of multi-spin interaction of a quenched XY chain by the average work and the relative entropy
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《中国物理 B》2021,30(9):90504-090504
We investigate the nonequilibrium thermodynamics of a quenched XY spin chain with multi-spin interaction in a transverse field. The analytical expressions of both the average work and the relative entropy are obtained under different quenching parameters. The influences of the system parameters on the nonequilibrium thermodynamics are investigated.We find that at finite temperature the critical phenomenon induced by the multi-spin interaction and the external field can be revealed by the properties of the system nonequilibrium thermodynamics. In addition, our results indicate that the average work and the relative entropy can be used to detect both the existence and strength of the multi-spin interaction in the nonequlibrium system. 相似文献
15.
Magnetotransport through an Aharonov-Bohm ring with parallel double quantum dots coupled to ferromagnetic leads
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Using the Keldysh nonequilibrium Green function and equation-of-motion
technique, this paper studies the magnetotransport through an Aharonov--Bohm (AB) ring with
parallel double quantum dots coupled to ferromagnetic leads. It calculates
the transmission probability in both the equilibrium and the nonequilibrium
case, analyses the conductance and the tunnel magnetoresistance for
various parameters, and obtains some new results. These results show that this
system is provided with an excellent spin filtering property, and that a large
tunnelling magnetoresistance and a negative tunnelling magnetoresistance can arise
by adjusting relative parameters; these facts indicate that this system is a
possible candidate for spin valve transistors, and has important
applications in spintronics. 相似文献
16.
E.I. Rashba 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):513-527
Insertion of a resistive contact between a ferromagnetic metal and a semiconductor microstructure is of critical importance
for achieving efficient spin injection into a semiconductor. However, the equations of the diffusion theory are rather cumbersome
for the junctions including such contacts. A technique based on deriving a system of self-consistent equations for the coefficients
of spin injection, γ, through different contacts are developed. These equations are concise when written in the proper notations.
Moreover, the resistance of a two-contact junction can be expressed in terms of γ's of both contacts. This equation makes
calculating the spin valve effect straightforward, allows to find an explicit expression for the junction resistance and to
prove that its nonequilibrium part is positive. Relation of these parameters to different phenomena like spin-e.m.f. and the
contact transients is established. Comparative effect of the Coulomb screening on different parameters is clarified. It is
also shown that the spin non-conservation in a contact can have a dramatic effect on the non-equilibrium resistance of the
junction.
Received 2 May 2002 / Received in final form 26 July 2002 Published online 15 October 2002
RID="a"
ID="a"Also at the Department of Physics, MIT, Cambridge, Massachusetts 02139, USA e-mail: erashba@mailaps.org 相似文献
17.
Based on the density functional theory and nonequilibrium Green's function methods, we investigate the spin transport properties of the molecular junctions constructed by a homologous series of 3d transition metal(II) salophens (TM-salophens, TM = Co, Fe, Ni and Mn) sandwiched between two gold electrodes. It is found that among the four molecular junctions only Co-salophen junction can act as an efficient spin filter distinctively. The conductance through Co-salophen molecular junction is dominated by spin-down electrons. The mechanism is proposed for these phenomena. 相似文献
18.
《Journal of magnetism and magnetic materials》2002,251(2):163-168
Taking into account the nonequilibrium spin accumulation, we apply a quantum-statistical approach to study the spin-polarized transport in a two-dimensional ferromagnet/semiconductor/ferromagnet (FM/SM/FM) double tunnel junction. It is found that the effective spin polarization is raised by increasing the barrier strength, resulting in an enhancement of the tunneling magnetoresistance (TMR). The nonequilibrium spin accumulation in SM may appear in both antiparallel and parallel alignments of magnetizations in two FMs, in particular for high bias voltages. The effects of spin accumulation and TMR on the bias voltage are discussed. 相似文献
19.
A spin device, consisting of parallel-coupled double quantum dots and three normal metal leads, is proposed to realize spin-polarized current without the help of magnetic field and magnetic material. Based on the Keldysh nonequilibrium Green function technique and equation of motion method, the spin-dependent current formula in each lead is derived. It is shown that not only a fully polarized current but also a tunable pure spin current can be obtained by modulating the structure parameters, strength of Rashba spin-orbit interaction and bias voltages properly. It further demonstrates the dependence of the spin-polarized current on the strength of the Rashba spin-orbit interaction. 相似文献
20.
In a ferromagnetic metal layer, the coupled charge and spin diffusion equations are obtained in the presence of both Rashba spin-orbit interaction and magnetism. The misalignment between the magnetization and the nonequilibrium spin density induced by the Rashba field gives rise to Rashba spin torque acting on the ferromagnetic order parameter. In a general form, we find that the Rashba torque consists of both in-plane and out-of-plane components, i.e., T=T(perpendicular)y^×m^+T(parallel)m^×(y^×m^). Numerical simulations on a two-dimensional nanowire consider the impact of diffusion on the Rashba torque and reveal a large enhancement to the ratio T(parallel)/T(perpendicular) for thin wires. Our theory provides an explanation for the mechanism driving the magnetization switching in a single ferromagnet as observed in the recent experiments. 相似文献