One of the long-standing goals of quantum transport is to use the noise, rather than the average current, for information processing. However, achieving this requires on-demand control of quantum fluctuations in the electric current. In this paper, we demonstrate theoretically that transport through a molecular spin-valve provides access to many different statistics of electron tunneling events. Simply by changing highly tunable parameters, such as electrode spin-polarization, magnetization angle, and voltage, one is able to switch between Poisson behavior, bunching and anti-bunching of electron tunnelings, and positive and negative temporal correlations. The molecular spin-valve is modeled by a single spin-degenerate molecular orbital with local electronic repulsion coupled to two ferromagnetic leads with magnetization orientations allowed to rotate relative to each other. The electron transport is described via Born-Markov master equation and fluctuations are studied with higher-order waiting time distributions. For highly magnetized parallel-aligned electrodes, we find that strong positive temporal correlations emerge in the voltage range where the second transport channel is partially open. These are caused by a spin-induced electron-bunching, which does not manifest in the stationary current alone.
We study frequency-dependent current noise through a single-level quantum dot connected to ferromagnetic leads with non-collinear magnetization. We propose to use the frequency-dependent Fano factor as a tool to detect single-spin dynamics in the quantum dot. Spin precession due to an external magnetic and/or a many-body exchange field affects the Fano factor of the system in two ways. First, the tendency towards spin-selective bunching of the transmitted electrons is suppressed, which gives rise to a reduction of the low-frequency noise. Second, the noise spectrum displays a resonance at the …
In quantum optics the $g^{(2)}$-function is a standard tool to investigate photon emission statistics. We define a $g^{(2)}$-function for electronic transport and use it to investigate the bunching and anti-bunching of electron currents. Importantly, we show that super-Poissonian electron statistics do not necessarily imply electron bunching, and that sub-Poissonian statistics do not imply anti-bunching. We discuss the information contained in $g^{(2)}(τ)$ for several typical examples of transport through nano-structures such as few-level quantum dots.
We observe and analyze tunable relaxation of a pure spin current by an antiferromagnet in spin-valves. This is achieved by carefully controlling the angle between a resonantly excited ferromagnetic layer pumping the spin current and the Néel vector of the antiferromagnetic layer. The effect is observed as an angle-dependent spin-pumping contribution to the ferromagnetic resonance linewidth. An interplay between spin-mixing conductance and, often disregarded, longitudinal spin conductance is found to underlie our observations, which is in agreement with a recent prediction for related ferromagn…
Current-driven spin torques in metallic spin-valves composed of antiferromagnets are theoretically studied using the non-equilibrium Green's function method implemented on a tight-binding model. We focus our attention on G-type and L-type antiferromagnets in both clean and disordered regimes. In such structures, spin torques can either rotate the magnetic order parameter coherently (coherent torque) or compete with the internal antiferromagnetic exchange (exchange torque). We show that, depending on the symmetry of the spin-valve, the coherent and exchange torques can be either in the plane, α…
Spin valves consisting of heterostructures of single-layer hexagonal crystal on an antiferromagnetic substrate or of bilayer hexagonal crystal intercalated between two (anti)ferromagnetic insulators, with the current-in-plane geometry, are proposed. The two-dimensional hexagonal crystals such as graphene, silicene, germanene, and stanene are modeled by the tight binding model of honeycomb lattice. The magnetization orientation of the antiferromagnetic substrate(s) controls the band gap and topological properties of bulk, which in turn control the transport of three types of spin valve geometri…
We consider current-induced spin-transfer torque on an antiferromagnet in a dual spin-valve setup. It is demonstrated that a net magnetization may be induced in the AFM by partially or completely aligning the sublattice magnetizations via a current-induced spin-transfer torque. This effect occurs for current densities ranging below 10$^6$ A/cm$^2$. The direction of the induced magnetization in the AFM is shown to be efficiently controlled by means of the magnetic configuration of the spin-valve setup, with the anti-parallell configuration yielding the largest spin-transfer torque. Interestingl…
We propose a spin valve that is based on van der Waals antiferromagnetism and fully electrically controlled. The device is composed of two antiferromagnetic terminals that allow for vertical bias control and a linked central scattering potential region. The magnetoresistance varies significantly when the bias orientations in two terminals are switched from parallel to antiparallel because this switch induces a mismatch of the bands for the same spin projection in different parts of the system. It is shown from density functional calculations that bilayer graphene encapsulated by two atomic lay…
We study the magnetic damping in the simplest of synthetic antiferromagnets, i.e. antiferromagnetically exchange-coupled spin valves in which applied magnetic fields tune the magnetic configuration to become noncollinear. We formulate the dynamic exchange of spin currents in a noncollinear texture based on the spindiffusion theory with quantum mechanical boundary conditions at the ferrromagnet|normal-metal interfaces and derive the Landau-Lifshitz-Gilbert equations coupled by the static interlayer non-local and the dynamic exchange interactions. We predict non-collinearity-induced additional d…
We use a ferromagnetic voltage probe model to study the influence of inelastic scattering on giant magnetoresistance and current-induced torques in ferromagnetic and antiferromagnetic metal spin valves. The model is based on the Green's function formulation of transport theory and represents spin-dependent and spin-independent inelastic scatterers by interior voltage probes that are constrained to carry respectively no charge current and no spin or charge current. We find that giant magnetoresistance and spin transfer torques in ferromagnetic metal spin valve structures survive arbitrarily str…
Switching field measurements of the free layer element of 75 nm diameter spin-valve nanopillars reveal a bimodal distribution of switching fields at low temperatures (below 100 K). This result is inconsistent with a model of thermal activation over a single perpendicular anisotropy barrier. The correlation between antiparallel to parallel and parallel to antiparallel switching fields increases to nearly 50% at low temperatures. This reflects random fluctuation of the shift of the free layer hysteresis loop between two different magnitudes, which may originate from changes in the dipole field f…
We consider a non-local spin valve in a Van der Pauw cross geometry with four ferromagnetic electrodes. Two antiparallel ferromagnets are used as (charge) source and drain while the detector circuit involves measuring the voltage between two collinear ferromagnets with parallel or antiparallel magnetizations. We find a potentially large increase of the non-local spin voltage. The setup displays several additional interesting properties: (i) infinite GMR for the non-local resistance (if a symmetry requirement for the device is met); (ii) ON-OFF switch effect, when the injector electrodes are pa…
We consider alignment-dependent spin and heat transport across a magnon spin valve in the tunneling regime, i.e., a junction consisting of two weakly coupled ferromagnetic insulators. We determine the difference in spin and heat conductance between the parallel and antiparallel configuration of the magnetization direction. The dependence of these conductances on both the Gilbert damping and ellipticity is studied. We find that both magnon ellipticity and dissipation open channels for magnons to tunnel through in the antiparallel configuration. Our results highlight an important difference betw…
Addressing the feasibility of quantum communication with entangled electrons in an interacting many-body environment, we propose an interference experiment using a scattering set-up with an entangler and a beam splitter. It is shown that, due to electron-electron interaction, the fidelity of the entangled singlet and triplet states is reduced by z_F^2 in a conductor described by Fermi liquid theory. We calculate the quasiparticle weight factor z_F for a two-dimensional electron system. The current noise for electronic singlet states turns out to be enhanced (bunching behavior), while it is red…
Spin transfer torque in spin valves usually destabilizes one of the collinear configurations (either parallel or antiparallel) and stabilizes the second one. Apart from this, balance of the spin-transfer and damping torques can lead to steady precessional modes. In this letter we show that in some asymmetric nanopillars spin current can destabilize both parallel and antiparallel configurations. As a result, stationary precessional modes can occur at zero magnetic field. The corresponding phase diagram as well as frequencies of the precessional modes have been calculated in the framework of mac…
Fluctuations of the magnetization in spin valves are shown to cause resistance noise that strongly depends on the magnetic configuration. Due to the applied external field and the dynamic exchange interaction through the normal metal spacer, the electrical noise level of the antiparallel configuration can exceed that of the parallel one by an order of magnitude, in agreement with recent experimental results.
We report a theoretical study on the spin and electron transport in the nonlocal lateral spin valve with non-collinear magnetic configuration. The nonlocal magnetoresistance, defined as the voltage difference on the detection lead over the injected current, is derived analytically. The spin transfer torques on the detection lead are calculated. It is found that spin transfer torques are symmetrical for parallel and antiparallel magnetic configurations, which is different from that in conventional sandwiched spin valve.
We study the quantum noise of electronic current in a double barrier system with a single resonant level. In the framework of the Landauer formalism we treat the double barrier as a quantum coherent scattering region that can exchange photons with a coupled electric field, e.g. a laser beam or a periodic ac-bias voltage. As a consequence of the manyfold parameters that are involved in this system, a complicated step-like structure arises in the non-symmetrized current-current auto correlation spectrum and a peak-like structure in the cross correlation spectrum with and without harmonic ac-driv…
We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure …
Spin selective nature of spin-filter tunnel junctions can be integrated with conventional metallic ferromagnets to regulate spin polarized quasiparticles in superconducting devices. We report fabrication of pseudo spin-valve device made with a bilayer of nitride spin-filter tunnel barrier (DyN or GdN) and a transition metal ferromagnet (Co and Gd). We show resistance switching in these devices corresponding to parallel and antiparallel configuration of their mutual magnetization direction. With optimal deposition process partial nitridation of the Co layer can be achieved. The magnetically dea…
In the present work we investigate the existence of multiple nonequilibrium steady states in a coherently driven XY lattice of dissipative two-level systems. A commonly used mean-field ansatz, in which spatial correlations are neglected, predicts a bistable behavior with a sharp shift between low- and high-density states. In contrast one-dimensional matrix product methods reveal these effects to be artifacts of the mean-field approach, with both disappearing once correlations are taken fully into account. Instead, a bunching-antibunching transition emerges. This indicates that alternative appr…
We report the free layer switching field distributions of spin-valve nanopillars with perpendicular magnetization. While the distributions are consistent with a thermal activation model, they show a strong asymmetry between the parallel to antiparallel and the reverse transition, with energy barriers more than 50% higher for the parallel to antiparallel transitions. The inhomogeneous dipolar field from the polarizer is demonstrated to be at the origin of this symmetry breaking. Interestingly, the symmetry is restored for devices with a lithographically defined notch pair removed from the midpo…
A most fundamental and longstanding goal in spintronics is to electrically tune highly efficient spin injectors and detectors, preferably compatible with nanoscale electronics. Here, we demonstrate all these points using semiconductor quantum dots (QDs), individually spin-polarized by ferromagnetic split-gates (FSGs). As a proof of principle, we fabricated a double QD spin valve consisting of two weakly coupled semiconducting QDs in an InAs nanowire (NW), each with independent FSGs that can be magnetized in parallel or anti-parallel. In tunneling magnetoresistance (TMR) experiments at zero ext…
Magnetization switching due to a current-pulse in symmetric and asymmetric spin valves is studied theoretically within the macrospin model. The switching process and the corresponding switching parameters are shown to depend significantly on the pulse duration and also on the interplay of the torques due to spin transfer and external magnetic field. This interplay leads to peculiar features in the corresponding phase diagram. These features in standard spin valves, where the spin transfer torque stabilizes one of the magnetic configurations (either parallel or antiparallel) and destabilizes th…
We experimentally demonstrate magnetostatic coupling between a nanopillar pseudo spin valve structure and a linear array of dipole coupled Permalloy nanomagnets. Using magnetic force microscopy, we study the interaction between the spin valve and the first element of the array, and present evidence that the nanomagnet couples with the hard layer of the spin valve for two spin valves with distinctly different composition. Our study includes a statistical analysis of antiferromagnetic order within the linear array, and provides insight into the range of behavior that these arrays can display. Th…
Spin-transfer torque in asymmetric spin valves can destabilize both parallel and antiparallel configurations and can lead to precessional modes also in the absence of an external magnetic field. We find a bistable precessional regime in such systems and show that thermal fluctuations can excite transitions (telegraph noise) between the corresponding oscillatory regimes that are well separated by irreversible paths at low temperatures. Because of the thermally induced transitions, the frequency of the resulting current-driven oscillations is different from that obtained at very low temperatures…
We present the first spintronic semiconductor field effect transistor. The injector and collector contacts of this device were made from magnetic permalloy thin films with different coercive fields so that they could be magnetized either parallel or antiparallel to each other in different applied magnetic fields. The conducting medium was a two dimensional electron gas (2DEG) formed in an AlSb/InAs quantum well. Data from this device suggest that its resistance is controlled by two different types of spin-valve effect: the first occurring at the ferromagnet-2DEG interfaces; and the second occu…
Graphene - a single atomic layer of graphite - is a recently-found two-dimensional form of carbon, which exhibits high crystal quality and ballistic electron transport at room temperature. Soft magnetic NiFe electrodes have been used to inject polarized spins into graphene and a 10% change in resistance has been observed as the electrodes switch from the parallel to the antiparallel state. This coupled with the fact that a field effect electrode can modulate the conductivity of these graphene films makes them exciting potential candidates for spin electronic devices.
We predict a new zero-bias anomaly in the differential conductance through a quantum dot coupled to two ferromagnetic leads with antiparallel magnetization. The anomaly differs in origin and properties from other anomalies in transport through quantum dots, such as the Kondo effect. It occurs in Coulomb-blockade valleys with an unpaired dot electron. It is a consequence of the interplay of single- and double-barrier cotunneling processes and their effect on the spin accumulation in the dot. The anomaly becomes significantly modified when a magnetic field is applied.
Magnetization dynamic response of coupled and uncoupled spin valves with structure NiFe(20 nm)/Cu(t_Cu)/NiFe(20 nm)/IrMn(10nm) were probed using broadband ferromagnetic resonance absorption measurements. By varying the Cu thickness t_Cu we were able to tailor the coupling intensity between the free and pinned layers. Broadband spectra show two resonant modes for each measured field. It is noticed that the coupling among NiFe layers modifies the amplitude of the absorption peaks and, moreover, the dispersion relations of the modes, which are distorted specially at the anti-parallel state. A num…
A quantum behavior of the light emitted by exciton polaritons excited in a pillar semiconductor microcavity with embedded quantum well is investigated. Considering the bare excitons and photon modes as coupled quantum oscillators allows for an accurate accounting of the nonlinear and dissipative effects. In particular, using the method of quantum states presentation in a quantum phase space via quasiprobability functions (namely, a $P$-function and a Wigner function), we study the effect of the laser and the exciton-photon detuning on the second order correlation function of the emitted photon…
Here, we present a study on Si(111)/\-Ta($150$Å)/\-IrMn($150$Å)/\-NiFe($50$Å)/\-Nb($x$)/\-NiFe($50$Å)/\-Ta($50$Å) and Si(111)/\-Ta($150$Å)/\-NiFe($50$Å)/\-Nb($x$)/\-NiFe($50$Å)/\-IrMn($150$Å)/\-Ta($50$Å) spin-valves with $x=100$ to $500$Å. For both sample families, above a specific critical thickness of the Nb-layer and below $T_c$, the superconducting Nb-layer contributes strongly to the magnetization. These systems show an anomalous hysteresis loop in the magnetization of the superconducting layer; the hysteresis loop is similar to what is generally expected from hard superconductors and man…
We show that the breakdown of the Wiedemann-Franz law due to electron--electron scattering in diffusive spin valves may result in a strong suppression of the Fano factor that describes the ratio between shot noise and average current. In the parallel configuration of magnetizations, we find the universal value $\sqrt{3}/4$ in the absence of a normal-metal spacer layer, but including the spacer leads to a non-monotonous suppression of this value before reaching back to the universal value for large spacer lengths. On the other hand, in the case of an antiparallel configuration with a negligibly…
We demonstrate the current-induced complete magnetization reversal of the free layer in lateral nanowires patterned from metallic pseudo spin valve stacks. The reversal is induced by Oersted fields in conjunction with a dipolar coupling via the lateral stray fields of the two magnetic layers. Starting from the parallel state the Oersted field rotates the magnetization vectors of both magnetic layers in opposite directions so far off the wire axis that the dipolar coupling becomes strong enough to stabilize an antiparallel configuration. As simulations and experiments show this coupling is only…
Vanadium based dichalcogenides, VSe$_2$, are two-dimensional materials in which magnetic Vanadium atoms are arranged in a hexagonal lattice and are coupled ferromagnetically within the plane. However, adjacent atomic planes are coupled antiferromagnetically. This provides new and interesting opportunities for application in spintronics and data storage and processing technologies. A spin valve magnetoresistance may be achieved when magnetic moments of both atomic planes are driven to parallel alignment by an external magnetic field. The resistance change associated with the transition from ant…
Motivated by the recent achievements in manipulation of C60 molecules in STM experiments, we study theoretically the structure and electronic properties of a C60 molecule in an STM-tunneljunction with a magnetic tip and magnetic adatom on a Cu(111) surface from first-principle calculations. For the case of V tip/adatom, we demonstrate how spin-coupling between the magnetic V atoms mediated by the C60 can be observed in the electronic transport, which display a strong spin-filtering effect, allowing mainly majority-spin electrons to pass(>95%). Moreover, we find a significant change in the cond…
A model of a spin valve in which electron transport between the magnetized electrodes is due to multistep tunneling is analyzed. Motivated by recent experiments on organic spin valves, we assume that spin memory loss in the course of transport is due to random hyperfine fields acting on electron while it waits for the next tunneling step. Amazingly, we identify the three-step configurations of sites, for which the tunnel magnetoresistance (TMR) is negative, suggesting that the resistance for antiparallel magnetizations of the electrodes is smaller than for parallel magnetizations. We analyze t…
This study theoretically investigated the magnetic properties and electronic structure of a graphene-based nano-spin-valve-like structure. Magnetic nickel layers on both sides of the graphene were considered. A spin-polarized generalized-gradient approximation determined the electronic states. In an energetically stable stacking arrangement of graphene and two nickel layers, the anti-parallel spin configuration of the underlayer and overlayer magnetic moments had the lowest energy, which is in agreement with previous experimental studies. The spin density mapping and obtained band-structure re…
We study the electrical injection and detection of spin accumulation in lateral ferromagnetic metal-nonmagnetic metal-ferromagnetic metal (F/N/F) spin valve devices with transparent interfaces. Different ferromagnetic metals, permalloy (Py), cobalt (Co) and nickel (Ni), are used as electrical spin injectors and detectors. For the nonmagnetic metal both aluminium (Al) and copper (Cu) are used. Our multi-terminal geometry allows us to experimentally separate the spin valve effect from other magneto resistance signals such as the anomalous magneto resistance (AMR) and Hall effects. We find that t…
We report time-resolved measurements of current-induced reversal of a free magnetic layer in Py/Cu/Py elliptical nanopillars at temperatures T = 4.2 K to 160 K. Comparison of the data to Landau-Lifshitz-Gilbert macrospin simulations of the free layer switching yields numerical values for the spin torque and the Gilbert damping parameters as functions of T. The damping is strongly T-dependent, which we attribute to the antiferromagnetic pinning behavior of a thin permalloy oxide layer around the perimeter of the free layer. This adventitious antiferromagnetic pinning layer can have a major impa…
Two-level fluctuations of the magnetization state of pseudo spin-valve pillars Co(10 nm)/Cu(10 nm)/Co(30 nm) embedded in electrodeposited nanowires (~40 nm in diameter, 6000 nm in length) are triggered by spin-polarized currents of 10^7 A/cm^2 at room temperature. The statistical properties of the residence times in the parallel and antiparallel magnetization states reveal two effects with qualitatively different dependences on current intensity. The current appears to have the effect of a field determined as the bias field required to equalize these times. The bias field changes sign when the…
We obtain photon statistics by using a quantum jump approach tailored to a system in which one or two qubits are coupled to a one-dimensional waveguide. Photons confined in the waveguide have strong interference effects, which are shown to play a vital role in quantum jumps and photon statistics. For a single qubit, for instance, bunching of transmitted photons is heralded by a jump that increases the qubit population. We show that the distribution and correlations of waiting times offer a clearer and more precise characterization of photon bunching and antibunching. Further, the waiting times…
To study spin flipping within the antiferromagnet IrMn, we extended prior Current-Perpendicular-to-Plane (CPP) Giant Magnetoresistance (GMR) studies of Py-based exchange-biased-spin-valves containing IrMn inserts to thicker IrMn layers-5 nm less than or equal to t(IrMn) less than or equal to 30 nm. Unexpectedly, AΔR = A[R(AP) - R(P)]--the difference in specific resistance between the anti-parallel (AP) and parallel (P) magnetic states of the two Py layers-did not decrease with increasing t(IrMn), for t(IrMn) greater than 5 nm, but rather became constant to within our measuring uncertainty. Thi…
We describe spin transfer in a ferromagnet/normal metal/ferromagnet spin-valve point contact. Spin is transferred from the spin-polarized device current to the magnetization of the free layer by the mechanism of incoherent magnon emission by electrons. Our approach is based on the rate equation for the magnon occupation, using Fermi's golden rule for magnon emission and absorption and the non-equilibrium electron distribution for a biased spin valve. The magnon emission reduces the magnetization of the free layer. For anti-parallel alignment of the magnetizations of the layers and at a critica…
A superconductor with a spin-split excitation spectrum behaves as an ideal ferromagnetic spin-injector in a tunneling junction. It was theoretical predicted that the combination of two such spin-split superconductors with independently tunable magnetizations, may be used as an ideal $absolute$ spin-valve. Here we report on the first switchable superconducting spin-valve based on two EuS/Al bilayers coupled through an aluminum oxide tunnel barrier. The spin-valve shows a relative resistance change between the parallel and antiparallel configuration of the EuS layers up to 900% that demonstrates…
We have studied the dependence of the superconducting (SC) transition temperature on the mutual orientation of magnetizations of Fe1 and Fe2 layers in the spin valve system CoO_x/Fe1/Cu/Fe2/Pb. We find that this dependence is nonmonotonic when passing from the parallel to the antiparallel case and reveals a distinct minimum near the orthogonal configuration. The analysis of the data in the framework of the SC triplet spin valve theory gives direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the two magnetizations.
We study the magnetoresistance of spin-valve devices using graphene as a non-magnetic material to connect ferromagnetic leads. As a preliminary step we first study the conductivity of a graphene strip connected to metallic contacts for a variety of lead parameters, and demonstrate that the resulting conductivity is rather insensitive to them. We then compute the conductivity of the spin-valve device in the parallel and antiparallel spin polarization configurations, and find that it depends only weakly on the relative spin orientations of the leads, so that the magnetoresistance $MR$ of the sys…
We have studied the proximity-induced superconducting triplet pairing in CoO$_x$/Py1/Cu/Py2/Cu/Pb spin-valve structure (where Py = Ni$_{0.81}$Fe$_{0.19}$). By optimizing the parameters of this structure we found a triplet channel assisted full switching between the normal and superconducting states. To observe an "isolated" triplet spin-valve effect we exploited the oscillatory feature of the magnitude of the ordinary spin-valve effect $ΔT_c$ in the dependence of the Py2-layer thickness $d_{Py2}$. We determined the value of $d_{Py2}$ at which $ΔT_c$ caused by the ordinary spin-valve effect (th…
Nonlinear current-voltage characteristics and magnetoresistance of point contacts between a normal metal (N) and films of amorphous ferromagnet (F) Co40Fe40B20 of different thickness, exchange-biased by antiferromagnetic Mn80Ir20 are studied. A surface spin valve effect in the conductance of such F-N contacts is observed. The effect of exchange bias is found to be inversely proportional to the Co40Fe40B20 film thickness. This behavior as well as other magneto-transport effects we observe on single exchange-pinned ferromagnetic films are similar in nature to those found in conventional three-la…
We study experimentally nanoscale Josephson junctions and Josephson spin-valves containing strong Ni ferromagnets. We observe that in contrast to junctions, spin valves with the same geometry exhibit anomalous Ic(H) patterns with two peaks separated by a dip. We develop several techniques for in-situ characterization of micromagnetic states in our nano-devices, including magnetoresistance, absolute Josephson fluxometry and First-Order-Reversal-Curves analysis. They reveal a clear correlation of the dip in supercurrent with the antiparallel state of a spin-valve and the peaks with two noncollin…
The magnetization detection and switching of an ultrasmall Stoner nanograin in a non-local spin valve (NLSV) device is studied theoretically. With the help of the rate equations, a unified description can be presented on the same footing for the NLSV signal that reads out the magnetization, and for the switching process. The setup can be viewed as that the grain is connected to two non-magnetic leads via sequential tunneling. In one lead, the chemical potentials for spin-up and -down electrons are split due to the spin injection in the NLSV. This splitting (or the spin bias) is crucial to the …
The spin transfer torque in all-metal dual spin valve, in which two antiparallelly aligned pinned ferromagnetic layers are on the two sides of a free ferromagnetic layer with two thin nonmagnetic spacers in between, is studied in the ballistic regime. It is argued that, similar to the results in the diffusion regime, the spin transfer torque is dramatically enhanced in comparison to that in a conventional spin valve although no spin accumulation exists at the magnetic-nonmagnetic interfaces. Within the Slonczewski's approach, an analytical expression of the torque on the free magnetic layer is…
We analyze the statistics of the electromagnetic radiation emitted from electrons pushed through a quantum point contact. We consider a setup implemented in a two-dimenional electron gas (2DEG) where the radiation manifests itself in terms of 2D plasmons emitted from electrons scattered at the point contact. The bosonic statistics of the plasmons competes with the fermionic statistics of the electrons; as a result, the quantum point contact emits non-classical radiation with a statistics which can be tuned from bunching to anti-bunching by changing the driving voltage. Our perturbative calcula…
