We study numerically the edge magnetoconductance of a quantum spin Hall insulator in the presence of quenched nonmagnetic disorder. For a finite magnetic field B and disorder strength W on the order of the bulk gap E_g, the conductance deviates from its quantized value in a manner which appears to be linear in |B| at small B. The observed behavior is in qualitative agreement with the cusp-like features observed in recent magnetotransport measurements on HgTe quantum wells. We propose a dimensional crossover scenario as a function of W, in which for weak disorder W < E_g the edge liquid is analogous to a disordered spinless 1D quantum wire, while for strong disorder W > E_g, the disorder causes frequent virtual transitions to the 2D bulk, where the originally 1D edge electrons can undergo 2D diffusive motion and 2D antilocalization.
Oscillatory variations of the diagonal ($G_{xx}$) and Hall ($G_{xy}$) magnetoconductances are discussed in view of topological scaling effects giving rise to the quantum Hall effect. They occur in a field range without oscillations of the density of states due to Landau quantization, and are, therefore, totally different from the Shubnikov-de Haas oscillations. Such oscillations are experimentally observed in disordered GaAs layers in the extreme quantum limit of applied magnetic field with a good description by the unified scaling theory of the integer and fractional quantum Hall effect.
The temperature driven flow lines of the diagonal and Hall magnetoconductance data (G_{xx},G_{xy}) are studied in heavily Si-doped, disordered GaAs layers with different thicknesses. The flow lines are quantitatively well described by a recent universal scaling theory developed for the case of duality symmetry. The separatrix G_{xy}=1 (in units e^2/h) separates an insulating state from a spin-degenerate quantum Hall effect (QHE) state. The merging into the insulator or the QHE state at low temperatures happens along a semicircle separatrix G_{xx}^2+(G_{xy}-1)^2=1 which is divided by an unstabl…
It is shown that the spin-orbit coupling due to structure inversion asymmetry leads to a characteristic anisotropy in the magnetoconductance of two-dimensional metals. Relevance for recent experiments is discussed.
Magnetotransport through cylindrical topological insulator (TI) nanowires is governed by the interplay between quantum confinement and geometric (Aharonov-Bohm and Berry) phases. Here, we argue that the much broader class of TI nanowires with varying radius -- for which a homogeneous coaxial magnetic field induces a varying Aharonov-Bohm flux that gives rise to a non-trivial mass-like potential along the wire -- is accessible by studying its simplest member, a TI nanocone. Such nanocones allow to observe intriguing mesoscopic transport phenomena: While the conductance in a perpendicular magnet…
In this work we have studied the parallel magnetoresistance of a 2DEG near a vicinal silicon surface. An unusual, linear magnetoconductance is observed in the fields up to $B = 15$ T, which we explain by the effect of spin olarization on impurity scattering. This linear magnetoresistance shows strong anomalies near the boundaries of the minigap in the electron spectrum of the vicinal system.
We identify theoretically the geometric phases of the electrons' spin that can be detected in measurements of charge and spin transport through Aharonov-Bohm interferometers threaded by a magnetic flux $Φ$ (in units of the flux quantum) in which both the Rashba spin-orbit and Zeeman interactions are active. We show that the combined effect of these two interactions is to produce a $\sin(Φ)$ [in addition to the usual $\cos(Φ)$] dependence of the magnetoconductance, whose amplitude is proportional to the Zeeman field. Therefore the magnetoconductance, though an even function of the magnetic fiel…
Signatures of spin-glass freezing such as the appearance of 1/f conductance noise, the recovery of universal conductance fluctuations, aging, as well as magnetic and thermal irreversibilities are detected in mesoscopic wires of CdMnTe:I at millikelvin temperatures. Spectral characteristics of conductance time series are consistent with the droplet model of short-range spin-glasses.
The spin-orbit interaction is a key tool for manipulating and functionalizing spin-dependent electron transport. However, the precise value of the spin-orbit coupling constant is hard to determine and control. Here we propose a measurement of the geometric (Aharonov-Casher) phase of the electron wavefunction generated by the spin-orbit coupling as a means to deduce the spin-orbit coupling strength in weak links. Unlike other proposed measurements of geometric phases, which rely on interference, we show that the anisotropy of the magnetoconductance, measured at different directions of an extern…
We present systematic quantitative description of the magnetoconductance of the split-gate quantum wires. Accounting for the exchange and correlation interactions within the spin density function theory (DFT) leads to the lifting of the spin degeneracy and formation of the spin-resolved plateaus at odd values of $e^{2}/h$. We show that the width of the odd conductance steps in the spin DFT calculations is equal to the width of the transition intervals between the conductance steps for the spinless electrons in the Hartree approximation. A detailed analysis of the structure of compressible/inco…
Graphene membranes suspended off electric contacts or other rigid supports are prone to elastic strain, which is concentrated at the edges and corners of the samples. Such a strain leads to an algebraically varying effective magnetic field that can reach a few Tesla in sub-micron wide flakes. In the quantum Hall regime the interplay of the effective and the physical magnetic fields causes backscattering of the chiral edge channels, which can destroy the quantized conductance plateaus.
In a recent Letter, Murzin et. al. [Phys. Rev. Lett., vol. 92, 016802 (2004)] investigated "instanton effects" in the magneto resistance data taken from samples with heavily Si-doped GaAs layers at low temperatures. This topological issue originally arose in the development of a microscopic theory of quantum Hall effect some 20 years ago. The investigations by Murzin et. al., however, do not convey the correct ideas on scaling that have emerged over the years in the general theory of quantum transport.
Polymer nanofibers are one-dimensional organic hydrocarbon systems containing conducting polymers where the non-linear local excitations such as solitons, polarons and bipolarons formed by the electron-phonon interaction were predicted. Magnetoconductance (MC) can simultaneously probe both the spin and charge of these mobile species and identify the effects of electron-electron interactions on these nonlinear excitations. Here we report our observations of a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI) and polythiophene (PT) nanofibers. In PA the MC is essentially…
We study the effects of spin-orbit coupling on the magnetoconductivity in diffusive cylindrical semiconductor nanowires. Following up on our former study on tubular semiconductor nanowires, we focus in this paper on nanowire systems where no surface accumulation layer is formed but instead the electron wave function extends over the entire cross section. We take into account the Dresselhaus spin-orbit coupling resulting from a zinc-blende lattice and the Rashba spin-orbit coupling, which is controlled by a lateral gate electrode. The spin relaxation rate due to Dresselhaus spin-orbit coupling …
We show that in the metallic phase of a two dimensional electron gas the spin-orbit coupling due to structure inversion asymmetry leads to a characteristic anisotropy in the magnetoconductance. Within the assumption that the metallic phase can be described by a Fermi liquid, we compute the conductivity in the presence of an in-plane magnetic field. Both the spin-orbit coupling and the Zeeman coupling with the magnetic field give rise to two spin subbands, in terms of which most of the transport properties can be discussed. The strongest conductivity anisotropy occurs for Zeeman energies of the…
Electron transport through multi-terminal rectangular arrays of quantum rings is studied in the presence of Rashba-type spin-orbit interaction (SOI) and of a perpendicular magnetic field. Using the analytic expressions for the transmission and reflection coefficients for single rings we obtain the conductance through such arrays as a function of the SOI strength, the magnetic flux, and of the wave vector $k$ of the incident electron. Due to destructive or constructive spin interferences caused by the SOI, the array can be totally opaque for certain ranges of $k$, while there are parameter valu…
We discuss the influence of the magneto-coulomb effect (MCE) on the magnetoconductance of spin valve devices. We show that MCE can induce magnetoconductances of several per cents or more, dependent on the strength of the coulomb blockade. Furthermore, the MCE-induced magnetoconductance changes sign as a function of gate voltage. We emphasize the importance of separating conductance changes induced by MCE from those due to spin accumulation in spin valve devices.
The transport properties of interacting electrons for which the spin degree of freedom is taken into account are numerically studied for small two dimensional diffusive clusters. On-site electron-electron interactions tend to delocalize the electrons, while long-range interactions enhance localization. On careful examination of the transport properties, we reach the conclusion that it does not show a two dimensional metal insulator transition driven by interactions. A parallel magnetic field leads to enhanced resistivity, which saturates once the electrons become fully spin polarized. The stre…
Edge states of the quantum Hall fluid provide an opportunity to study mesoscopic effects in a highly correlated electron system that is both experimentally accessible and theoretically tractable. In this paper we review recent work on the persistent current and Aharonov-Bohm magnetoconductance oscillations in the fractional quantum Hall effect regime.
We investigated the magnetotransport of InAs nanowires grown by selective area metal-organic vapor phase epitaxy. In the temperature range between 0.5 and 30 K reproducible fluctuations in the conductance upon variation of the magnetic field or the back-gate voltage are observed, which are attributed to electron interference effects in small disordered conductors. From the correlation field of the magnetoconductance fluctuations the phase-coherence length l_phi is determined. At the lowest temperatures l_phi is found to be at least 300 nm, while for temperatures exceeding 2 K a monotonous decr…
We calculate the Andreev conductance of a superconducting ring interrupted by a flux-biased Josephson junction, searching for electrical signatures of circulating edge states. Two-dimensional pair potentials of spin-singlet d-wave and spin-triplet p-wave symmetry support, respectively, (chiral) Dirac modes and (chiral or helical) Majorana modes. These produce h/e-periodic magnetoconductance oscillations of amplitude \simeq (e^{2}/h)N^{-1/2}, measured via an N-mode point contact at the inner or outer perimeter of the grounded ring. For Dirac modes the oscillations in the two contacts are indepe…
Semiconductor Bi$_2$O$_2$Se nanolayers of high crystal quality have been realized via epitaxial growth. These two-dimensional (2D) materials possess excellent electron transport properties with potential application in nanoelectronics. It is also strongly expected that the 2D Bi$_2$O$_2$Se nanolayers could be of an excellent material platform for developing spintronic and topological quantum devices, if the presence of strong spin-orbit interaction in the 2D materials can be experimentally demonstrated. Here, we report on experimental determination of the strength of spin-orbit interaction in …
The edge states of two-dimensional time-reversal topological insulators support a perfect helical conductance on wide ribbons due to the absence of backscattering. Here, we study the changes in the transport properties of topological insulator nanoribbons by introducing a constriction along the ribbon. This setup allows the edge states to hybridize, leading to reflections at the ends of the constriction. We find that the electronic states running along one edge can be reflected back along the opposite edge multiple times, giving rise to Fabry-Pérot resonant vortices within the constriction wit…
The temperature driven flow lines of the Hall and dissipative magnetoconductance data (σ_{xy},σ_{xx}) are studied in the fractional quantum Hall regime for a 2D electron system in GaAs/Al_{x}Ga_{1-x}As heterostructures. The flow lines are rather well described by a recent unified scaling theory developed for both the integer and the fractional quantum Hall effect in a totally spin-polarized 2D electron system which predicts that one (σ_{xy},σ_{xx}) point determines a complete flow line.
The current in response to a bias in certain two-dimensional electron gas (2DEG), can have a nonzero transverse component under a finite magnetic field applied in the plane where electrons are confined. This phenomenon known as planar Hall effect is accompanied by dependencies of both the longitudinal and the transverse components of the current on the angle $ϕ$ between the bias direction and the magnetic field. In 2DEG with spin orbit coupling (SOC) such as oxide interfaces, this effect has been experimentally witnessed. Further, a fourfold oscillation in longitudinal resistance as a function…
We construct a theory of coherent transport through a ballistic quantum dot coupled to a superconductor. We show that the leading-order quantum correction to the two-terminal conductance of these Andreev quantum dots may change sign depending on (i) the number of channels carried by the normal leads or (ii) the magnetic flux threading the dot. In contrast, spin-orbit interaction may affect the magnitude of the correction, but not always its sign. Experimental signatures of the effect include a non-monotonic magnetoconductance curve and a transition from an insulator-like to a metal-like temper…
We use magnetoconductance measurements in dual-gated InSb nanowire devices together with a theoretical analysis of weak antilocalization to accurately extract spin-orbit strength. In particular, we show that magnetoconductance in our three-dimensional wires is very different compared to wires in two-dimensional electron gases. We obtain a large Rashba spin-orbit strength of $0.5 -1\,\text{eVÅ}$ corresponding to a spin-orbit energy of $0.25-1\,\text{meV}$. These values underline the potential of InSb nanowires in the study of Majorana fermions in hybrid semiconductor-superconductor devices.
The conductance of a two-dimensional electron gas at the transition from one quantum Hall plateau to the next has sample-specific fluctuations as a function of magnetic field and Fermi energy. Here we identify a universal feature of these mesoscopic fluctuations in a Corbino geometry: The amplitude of the magnetoconductance oscillations has an e^2/h resonance in the transition region, signaling a change in the topological quantum number of the insulating bulk. This resonance provides a signed scaling variable for the critical exponent of the phase transition (distinct from existing positive de…
We investigate the transport properties of high-quality single-layer graphene, epitaxially grown on a 6H-SiC(0001) substrate. We have measured transport properties, in particular charge carrier density, mobility, conductivity and magnetoconductance of large samples as well as submicrometer-sized Hall bars which are entirely lying on atomically flat substrate terraces. The results display high mobilities, independent of sample size and a Shubnikov-de Haas effect with a Landau level spectrum of single-layer graphene. When gated close to the Dirac point, the mobility increases substantially, and …
Low temperature magnetoconductance measurements were made in the vicinity of the charge neutrality point. Two origins for the fluctuations were identified close to the CNP. At very low magnetic fields there exist only mesoscopic magneto-conductance quantum interference features which develop rapidly as a function of density. At slightly higher fields (> 0.5T), close to the CNP, additional fluctuations track the quantum Hall sequence expected for monolayer graphene. These additional features are attributed to effects of locally charging individual quantum Hall (QH) localized states. These effec…
The thickness dependence of spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers is studied using the first-principles non-equilibrium Green's function formalism combined with the Anderson disorder model. A systematic expansion in orthogonal vector spherical harmonics is used for the angular dependence of the torque. The damping-like torque in Co/Pt and Co/Au bilayers can be described as a sum of the spin-Hall contribution, which increases with thickness in agreement with the spin-diffusion model, and a comparable interfacial contribution. The magnetoconductance in the p…
In this paper we report on the observation of very high and narrow magnetoconductance peaks which we attribute to the transition to quantum Hall ferromagnet (QHFM) state occurring at the edges of the sample. We show that the expected spatial degeneracy of chiral edge channels is spontaneously lifted in agreement with theoretical studies performed within the Hartree-Fock approximation. We indicate also that separated edge currents which flow in parallel, may nevertheless cross at certain points, giving rise to the formation of topological defects or one-dimensional magnetic domains. Furthermore…
Competition between liquid and solid states in two-dimensional electron system is an intriguing problem in condensed matter physics. We have investigated competing Wigner crystal and fractional quantum Hall ( FQH ) liquid phases in atomically thin suspended graphene devices in Corbino geometry. Low temperature magnetoconductance and transconductance measurements along with $IV$ characteristics all indicate strong charge density dependent modulation of electron transport. Our results show unconventional FQH phases which do not fit the standard Jain's series for conventional FQH states, instead …
We analyze the effect of weak localization (WL) and weak antilocalization (WAL) in the electronic transport through HgTe/CdTe quantum wells. We show that for increasing Fermi energy the magnetoconductance of a diffusive system with inverted band ordering features a transition from WL to WAL and back, if spin-orbit interactions from bulk and structure inversion asymmetry can be neglected. This, and an additional splitting in the magnetoconductance profile, is a signature of the Berry phase arising for inverted band ordering and not present in heterostructures with conventional ordering. In pres…
We use spin-density-functional theory within an envelope function approach to calculate electronic states in a GaAs/InAs core-shell nanowire pierced by an axial magnetic field. Our fully 3D quantum modeling includes explicitly the description of the realistic cross-section and composition of the sample, and the electrostatic field induced by external gates in two different device geometries, gate-all-around and back-gate. At low magnetic fields, we investigate Aharonov-Bohm oscillations and signatures therein of the discrete symmetry of the electronic system, and we critically analyze recent m…
We offer a new perspective to the problem of characterizing mesoscopic fluctuations in the inter-plateau region of the integer quantum Hall transition. We found that longitudinal and transverse conductance fluctuations, generated by varying the external magnetic field within a microscopic model, are multifractal and lead to distributions of conductance increments (magnetoconductance) with heavy tails (intermittency) and signatures of a hierarchical structure (a cascade) in the corresponding stochastic process, akin to Kolmogorov's theory of fluid turbulence. We confirm this picture by interpre…
We have obtained numerically exact results for the spin-related geometric quantum phases that arise in p-type semiconductor ring structures. The interplay between gate-controllable (Rashba) spin splitting and quantum-confinement-induced mixing between hole-spin states causes a much higher sensitivity of magnetoconductance oscillations to external parameters than previously expected. Our results imply a much-enhanced functionality of hole-ring spin-interference devices and shed new light on recent experimental findings.
We have studied the ground and excited state spectra of a semiconductor quantum dot for successive numbers of electron occupancy using linear and nonlinear magnetoconductance measurements. We present the first observation of direct correlation between the mth excited state of the N electron system and the ground state of the N+m electron system for m up to 4. Results are consistent with a non-spin-degenerate single particle picture of the filling of levels. Electron-electron interaction effects are also observed as a perturbation to this model. Magnetoconductance fluctuations of ground states …
We present an open version of the symplectic kicked rotator as a stroboscopic model of electrical conduction through an open ballistic quantum dot with spin-orbit scattering. We demonstrate numerically and analytically that the model reproduces the universal weak localization and weak anti-localization peak in the magnetoconductance, as predicted by random-matrix theory (RMT). We also study the transition from weak localization to weak anti-localization with increasing strength of the spin-orbit scattering, and find agreement with RMT.
A new kind of charge-Hall effect is shown. Unlike in the usual Hall effect, the driving force in the longitudinal direction is a spin force, which may originate from the gradient of a Zeeman field or a spin-dependent chemical potential. The transverse force is provided by a Berry curvature in a mixed position-momentum space. We can establish an Onsager relation between this effect and the spin-Hall effect provided the spin current in the latter is modified by a torque dipole contribution. This remarkable relation leads to new ways for experimental detection of spin accumulation predicted by th…
The spin Hall effect does not generally result in a charge Hall voltage. We predict that in systems with inhomogeneous electron density in the direction perpendicular to main current flow, the spin Hall effect is instead accompanied by a Hall voltage. Unlike the ordinary Hall effect, we find that this Hall voltage is quadratic in the longitudinal electric field for a wide range of parameters accessible experimentally. We also predict spin accumulation in the bulk and sharp peaks of spin-Hall induced charge accumulation near the edges. Our results can be readily tested experimentally, and would…
We develop a semiclassical theory for spin-dependent quantum transport to describe weak (anti)localization in quantum dots with spin-orbit coupling. This allows us to distinguish different types of spin relaxation in systems with chaotic, regular, and diffusive orbital classical dynamics. We find, in particular, that for typical Rashba spin-orbit coupling strengths, integrable ballistic systems can exhibit weak localization, while corresponding chaotic systems show weak antilocalization. We further calculate the magnetoconductance and analyze how the weak antilocalization is suppressed with de…
We report electron transport studies in an encapsulated few-layer WTe$_2$ at low temperatures and high magnetic fields. The magnetoconductance reveals a temperature-induced crossover between weak antilocalization (WAL) and weak localization (WL) in quantum diffusive regime. We show that the crossover clearly manifests coexistence and competition among several characteristic lengths, including the dephasing length, the spin-flip length, and the mean free path. In addition, low temperature conductance increases logarithmically with the increase of temperature indicating an interplay of electron-…
Magnetoconductance of a gated two-dimensional electron gas (2DEG) in the inversion layer on p-type HgCdTe crystal is investigated. At strong magnetic fields, characteristic features such as quantum Hall effect of a 2DEG with single subband occupation are observed. At weak magnetic fields, weak antilocalization effect in ballistic regime is observed. Phase coherence time and zero-field spin-splitting are extracted according to Golub's model. The temperature dependence of dephasing rate is consistent with Nyquist mechanism including both singlet and triplet channel interactions.
We theoretically investigate the role of spin fluctuations in charge transport through a magnetic junction. Motivated by recent experiments that measure a nonlinear dependence of the current on electrical bias, we develop a systematic understanding of the interplay of charge and spin dynamics in nanoscale magnetic junctions. Our model captures two distinct features arising from these fluctuations: magnon-assisted transport and the effect of spin-transfer torque on the magnetoconductance. The latter stems from magnetic misalignment in the junction induced by spin-current fluctuations. As the te…
The interplay of exchange correlations and spin-orbit interaction (SOI) on the many-body spectrum of a copper phtalocyanine (CuPc) molecule and their signatures in transport are investigated. We first derive a minimal model Hamiltonian in a basis of frontier orbitals which is able to reproduce experimentally observed singlet-triplet splittings; in a second step SOI effects are included perturbatively. Major consequences of the SOI are the splitting of former degenerate levels and a magnetic anisotropy, which can be captured by an effective low-energy spin Hamiltonian. We show that STM-based ma…
We show that in van der Waals stacks of twisted hexagonal layers the proximity induced Rashba spin-orbit coupling can be affected by quantum interference. We calculate the quantum phase responsible for this effect in graphene--transition metal dichalcogenide bilayers as a function of interlayer twist angle. We show how this quantum phase affects the spin-polarization of the graphene bands and discuss its potential effect on spin-to-charge conversion measurements. In twisted trilayers symmetries can be broken as well as restored for certain twist angles. This can be used to deduce the effects o…
Harmonic Hall voltage measurements are a wide-spread quantitative technique for the measurement of spin-orbit induced effective fields in heavy-metal / ferromagnet heterostructures. In the vicinity of the voltage pickup lines in the Hall bar, the current is inhomogeneous, which leads to a hitherto not quantified reduction of the effective fields and derived quantities, such as the spin Hall angle or the spin Hall conductivity. Here we present a thorough analysis of the influence of the aspect ratio of the voltage pickup lines to current channel widths on the apparent spin Hall angle. Experimen…
Spin Hall effect in a nonlocal spin-injection device is theoretically studied. Using a nonlocal spin-injection technique, a pure spin current is created in a nonmagnetic metal (N). The spin current flowing in N is deflected by spin-orbit scattering to induce the Hall current in the transverse direction and accumulate charge at the edges of N, yielding the spin-current induced Hall effect. We propose a method for extracting information for spin-orbit scattering in nonmagnetic metals.
It is proposed that the new generation of spintronics should be ideally massless and dissipationless for the realization of ultra-fast and ultra-low-power spintronic devices. We demonstrate that the spin-gapless materials with linear energy dispersion are unique materials that can realize these massless and dissipationless states. Furthermore, we propose four new types of spin Hall effects which consist of spin accumulation of equal numbers of electrons and holes having the same or opposite spin polarization at the sample edge in Hall effect measurements, but with vanishing Hall voltage. These…
We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically 3 graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H-SiC, and characterized by surface-science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kOhm to 225 kOhm at 4 K, with positive magnetoconductance). Low resistance samples show characteristics of weak-localization in two dimensions, from which we estimate elastic and inelastic mean fr…
The intrinsic spin Hall effect (SHE) originates from the topology of the Bloch bands in momentum space. The duality between real space and momentum space calls for a spin Hall effect induced from a real space topology in analogy to the topological Hall effect (THE) of skyrmions. We theoretically demonstrate the topological spin Hall effect (TSHE) in which a pure transverse spin current is generated from a skyrmion spin texture.
The spin Hall angle (SHA) is a measure of the efficiency with which a transverse spin current is generated from a charge current by the spin-orbit coupling and disorder in the spin Hall effect (SHE). In a study of the SHE for a Pt$|$Py (Py=Ni$_{80}$Fe$_{20}$) bilayer using a first-principles scattering approach, we find a SHA that increases monotonically with temperature and is proportional to the resistivity for bulk Pt. By decomposing the room temperature SHE and inverse SHE currents into bulk and interface terms, we discover a giant interface SHA that dominates the total inverse SHE current…
We propose a mechanism of intrinsic spin Hall effect (SHE). In this mechanism, local orbital angular momentum (OAM) induces electron position shift and couples with the bias electric field to generate orbital Hall effect (OHE). SHE then emerges as a concomitant effect of OHE through the atomic spin-orbit coupling. Spin Hall conductivity due to this mechanism is estimated to be comparable to experimental values for heavy metals. This mechanism predicts the sign change of the spin Hall conductivity as the spin-orbit polarization changes its sign, and also correlation between the spin Hall conduc…
Conceptual framework behind the intrinsic spin Hall effect in three-dimensional conductors is discussed. Theory suggests how the spin Hall current should depend on symmetry and orientation of the crystal.
Relativistic band theoretical calculations reveal that intrinsic spin Hall conductivity in hole-doped archetypical semiconductors Ge, GaAs and AlAs is large $[\sim 100 (\hbar/e)(Ωcm)^{-1}]$, showing the possibility of spin Hall effect beyond the four band Luttinger Hamiltonian. The calculated orbital-angular-momentum (orbital) Hall conductivity is one order of magnitude smaller, indicating no cancellation between the spin and orbital Hall effects in bulk semiconductors. Furthermore, it is found that the spin Hall effect can be strongly manipulated by strains, and that the $ac$ spin Hall conduc…
Spin pumping in ferromagnets provides a source of pure spin currents. Via the inverse spin Hall effect a spin current is converted into a charge current and a corresponding detectable DC-voltage. The ratio of injected spin current to resulting charge current is given by the spin Hall angle. However, the number of experiments more or less equals the number of different values for spin Hall angles, even for the most studied normal metal platinum. This publication provides a full study of inverse spin Hall effect and anisotropic magnetoresistance for different NiFe(Py) / normal metal bilayers usi…
