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Combining theory and computation, we explore the Goos–Hänchen (GH) effect for electrons in a single-layered semiconductor microstructure (SLSM) modulated by Dresselhaus spin–orbit coupling (SOC). GH displacement depends on electron spins thanks to Dresselhaus SOC, therefore electron spins can be separated from the space domain and spin-polarized electrons in semiconductors can be realized. Both the magnitude and sign of the spin polarization ratio change with the electron energy, in-plane wave vector, strain engineering and semiconductor layer thickness. The spin polarization ratio approaches a maximum at resonance; however, no electron-spin polarization occurs in the SLSM for a zero in-plane wave vector. More importantly, the spin polarization ratio can be manipulated by strain engineering or semiconductor layer thickness, giving rise to a controllable spatial electron-spin splitter in the field of semiconductor spintronics. [ABSTRACT FROM AUTHOR]

In the field of ultrafast magnetism, i.e., subpicosecond or femtosecond time scales, the dynamics of magnetization can be described by the inertial Landau–Lifhitz–Gilbert equation. In terms of this equation, the intrinsic characteristics are investigated in detail for the theoretical limit of the magnetization reversal field. We can find that there is a critical value for the inertia parameter τ c, which is affected by the damping and anisotropy parameter of the system. When the inertial parameter factor τ < τ c, the limit value of the magnetization reversal field under the ultrafast magnetic mechanism is smaller than that of the fast magnetic mechanism. When τ > τ c, the limit value of the magnetization reversal field will be larger than the limit value under the fast magnetic mechanism. Moreover, it is important to point out that the limit value of the magnetization reversal field under the ultrafast magnetic mechanism decreases with the increasing inertial factor, as τ < τ c/2, which increases with inertial factor τ as τ > τ c/2. Finally, with the joint action of damping and anisotropy, compared with fast magnetism, we find that the limit value of the magnetization reversal field has rich variation characteristics, i.e., there is not only a linear and proportional relationship, but also an inverse relationship, which is very significant for the study of ultrafast magnetism. [ABSTRACT FROM AUTHOR]

Spin-dependent resonance polarisation in CdTe / CdMnTe double-barrier heterostructure was theoretically examined. The effects of Zeeman effect (ZE), giant Zeeman effect (GZE) and Dresselhaus spin–orbit interaction (DSOI) were analysed in the presence of electric and magnetic fields. The heterostructure transition from type-I to type-II enhances the spin-down heavy hole current density. The results indicate that this heterostructure works as a perfect spin-down heavy hole filter. [ABSTRACT FROM AUTHOR]

In the present work, a tuned quantum dot / ring system under both external magnetic and electric fields is studied. The energy eigenvalues and wave functions are analytically derived. Then, an analytical expression for the Stark shift is obtained. The results reveal that: (i) The ground state and excited state energies at large and small electric fields show various behaviours, (ii) the ground and excited state energies reduce by raising the electric field and (iii) the ground and excited state energies increase by enhancing the system size. Our model can be transformed into a two-dimensional (2D) quantum disk or a 2D quantum ring. The results show that the Stark shifts at low and high electric fields vary. The behaviour depends strongly on the magnetic field and the system size. [ABSTRACT FROM AUTHOR]

Magnetic state is a partial ordered state if only part of the electrons in the system give contribution to the magnetic order. We study Heisenberg model of two sublattice spin system, on the body-centered cubic lattice, with antiferromagnetic nearest neighbors exchange of sublattice A and B spins and two different ferromagnetic exchange constants for sublattice A (J A) and B (J B) spins. When J A > J B the system undergoes transition from paramagnetism to ferromagnetism at Curie temperature T C. Only the sublattice A spins give contribution to the magnetization of the system. Upon cooling, the system possesses ferromagnetism to antiferromagnetism transition at Néel temperature T N < T C. Below T N sublattice A and B electrons give contribution to the magnetization. The transition is a partial ordered transition. There is thermodynamic evidence for this transition in the magnetic specific heat of the system. As a function of temperature there are two maxima. At high temperature T C it is λ -type. At lower temperature T N it characterizes the transition from ferromagnetism to antiferromagnetism. As an example of ferromagnetism to antiferromagnetism partial ordered transition we consider the material L a 1 − x C a x M n O 3 in the doping range x ≥ 0.50. Our calculations reproduce the experimental magnetization-temperature curve. • Antiferromagnetism to ferromagnetism transition. • Partial order transition. • Transition triggered by charge ordering in La(1-x)Ca(x)MnO(3). • Transition in La(1-x)Ca(x)MnO(3) is Partial order transition. [ABSTRACT FROM AUTHOR]

Quantum transmission through a heterojunction formed by two types of nodal‐line semimetals is investigated. Results show that the initial energy and energy range of the quantum transmission can be modulated efficiently when the barrier region demonstrates its different energy‐band properties. Antiresonance points can also appear in the transmission function spectra. Moreover, if the barrier is parallel to the basal planes of the nodal‐line semimetals, one gap appears in the transmission function spectrum instead of the normal antiresonance point. In addition, the Klein tunneling displays new characteristics in such a heterojunction. All these results provide useful information for adjusting the transmission behaviors in the heterojunctions of nodal‐line semimetals. [ABSTRACT FROM AUTHOR]

Non-uniform height semiconductor quantum rings are studied in order to determine their electronic and optical absorption properties. Theoretical modelling of the structure includes an analytical description of the non-regular multi-hilled confining potential as well as the presence of repulsive scattering centre and external crossing electric and magnetic fields. We have discussed the features of localised and extended (rotational, Aharonov–Bohm-like) states in the presence of the magnetic field. A modification of the spectrum, with the appearance of a Stark-like behaviour, and its corresponding modification related to the repulsive potential is analysed when the electric field effect is considered. In double-hilled structures, these properties of the energy spectrum are of main importance in explaining the apparent optical transparency induced within a certain range of the electric field strength. The presence of the repulsive centre is found to cause a moderate redshift of the light absorption response. [ABSTRACT FROM AUTHOR]

Voltage control of magnetism promises great energy efficiency in writing magnetic memory. Here, using Cr/Mo/CoFeB/MgO multilayers stable under high annealing temperatures up to 590°C, we significantly enhance the interfacial crystallinity, thereby the interface-originated perpendicular magnetic anisotropy (PMA), voltage-controlled magnetic anisotropy (VCMA), and interface magnetoelectric (ME) effect. High interfacial PMA of 1.35 mJ/m2, VCMA coefficient of −138 fJ/(V m), and interface ME coefficient, which is 2–3 orders of magnitude larger than ab initio calculation results are simultaneously achieved after annealing at 500°C. These promising results enabled by the industry-applicable sputtering process will pave the way for high-density voltage-controlled spintronic devices. [ABSTRACT FROM AUTHOR]

The influence of magnetic field and Coulomb field on the Rashba spin–orbit interaction in a triangular quantum well was studied using Pekar variational method. We theoretically derived the expression of the bound magnetopolaron ground-state energy. The energy of the bound magnetopolaron splits under the influence of the Rashba effect. From this phenomenon, it is concluded that the effects of orbital and spin interactions on the polaron energy in different directions must be considered. Because of the contribution of the magnetic field cyclotron resonance frequency to the Rashba spin–orbit splitting, the energy spacing becomes larger as the magnetic field cyclotron resonance frequency increases. Compared to the bare electron, the bound polaron is more stable, and the energy of bound polaron split is more stable. [ABSTRACT FROM AUTHOR]

We study the ground-state lifetime (GSL) of polaron in a two-dimensional RbCl quantum pseudodot (QPD) system by using a variational method of Pekar type (PTVM) and the quantum statistical theory. Considering the polaron effect, we derive the dependent relations of the temperature, the electric field, the chemical potential (CP) of the two-dimensional electron gas (TDEG), the polaron radius (PR) and the zero point (ZP) of the pseudoharmonic potential (PHP) on the GSL of polaron. The calculated results show that the GSL τ of polaron will decrease when the CP V 0 of the TDEG, the electric field and the PR R p increase, but will increase while the ZP r 0 of the PHP, the ground-state energy (GSE) and the temperature parameter γ become larger, respectively. That means that by changing the electric field, the temperature, the PR, the CP of the TDEG and the ZP of the PHP, one can adjust the GSL of polaron, which may offer new insight into studying many related applications in quantum computation (QC) and control of electron transition. [ABSTRACT FROM AUTHOR]

We analyze, in exact terms, multiband 2D itinerant correlated fermionic systems with many-body spin-orbit interactions, and in-plane external magnetic fields. Even if such systems with broad applicability in leading technologies are non-integrable, we set up an exact solution procedure for them, which is described in details. Casting the Hamiltonian in positive semidefinite form, the technique leads to the ground state, and also characterises the low lying excitation spectrum. [ABSTRACT FROM AUTHOR]

Neutron powder diffraction and magnetization measurements have been performed for La0.7Sr0.3Mn0.7Ti0.3-xAlxO3 (0 = x = 0.15) stoichiometric compounds. Increase of the Al3+ content enlarges the Mn4+ ions fraction from 0% (x=0) up to around 20% (x=0.15). The x=0 composition around 150 K exhibits a structural transition from the rhombohedral phase to the orthorhombic one whereas the crystal structure of the compounds with x=0.1 and 0.15 remains to be rhombohedral down to 2 K. The substitution of Ti4+ by Al3+ ions is accompanied by a gradual increase in the bond angle Mn-O-Mn and decrease in the Mn-O bond length which lead to enhancement of the covalent component of the chemical bond. All these compounds exhibit ferromagnetic components below 100 K. Magnetic moments estimated per manganese from the neutron powder diffraction data are found to be around 1.3 µB (x=0) and 1.7 µB (x=0.1 and 0.15) at 2 K. It is suggested that ferromagnetism is originated predominantly from the Mn3+-O-Mn3+ and Mn3+-O-Mn4+ superexchange interactions whereas bond angles fluctuation leads to magnetic frustrations. Enhancement of covalence slightly increases ferromagnetism. [ABSTRACT FROM AUTHOR]

On the basis of Lee-Low-Pines unitary transformation, the influences of Rashba spin-orbit (RSO) coupling energy and Zeeman splitting energy on the ground-state energy of polaron in a quantum rod (QRD) have been studied by using a variational method of Pekar type. Taking the RSO interaction and the Zeeman splitting into account, we derive the variational relations of the absolute ratios $$ \zeta_{1} $$ and $$ \zeta_{2} $$ of the RSO coupling energy and the Zeeman splitting energy to the ground-state energy of polaron with the transverse confinement radius (TCR) and the longitudinal confinement length (LCL) of QRD, as well as and the magnetic field adjusting length (MFAL). The results show that the absolute ratios $$ \zeta_{1} $$ and $$ \zeta_{2} $$ will increase when the TCR and the LCL become larger, but will slowly decrease while the MFAL and the aspect ratio of the ellipsoid $$ \delta $$ increase, respectively. The above results can be attributed to the spin effects and interesting quantum size confining. [ABSTRACT FROM AUTHOR]

The conventional spin-orbit interaction due to the presence of a central or off-central impurity located in a multilayered spherical quantum dot (MSQD) has been investigated. The different effective masses of dots and barriers have been taken into consideration. The spin-orbit interaction has been calculated in the excited state (2 p). The variational method has been applied by using a new form of the trial wave function in addition to the conventional form that has been used in previous work. The new form has the advantage of satisfying the boundary conditions at the interfaces between dots and barriers in the case of different masses. The case of central impurity has been further explored by using the exact analytical solution in the state (2 p) of the radial Schrödinger equation in the presence of the impurity. Moreover, the calculations have been performed in the case of a MSQD of thin inner barrier, for which the electron is most probably localized in the outer dot. Thus for an off-central impurity placed in the inner dot the spin-orbit energy increases continuously as the impurity location moves towards the surface of the inner dot. The study has yielded new analytical expressions for the electron energy, binding energy and spin-orbit expectation energy for both central and off-central impurities. [ABSTRACT FROM AUTHOR]

Noncentrosymmetric superconductors (NCSs) with broken inversion symmetry can have spin-dependent order parameters (OPs) with mixed parity which can also have nodes in the pair potential as well as the energy spectra. These nodes are distinct features that are not present in conventional superconductors. They appear as points or lines in the momentum space where the latter can have angular or radial geometries dictated by the dimensionality, the lattice structure and the pairing interaction. In this work we study the nodes in time reversal symmetry (TRS) preserving NCSs at the OP, the pair potential, and the energy spectrum levels. Nodes are examined by using spin independent pairing interactions respecting the rotational C ∞ v symmetry in the presence of spin-orbit coupling (SOC). The pairing symmetries and the nodal topology are affected by the relative strength of the pairing channels which is studied for the mixed singlet-triplet, pure singlet, and pure triplet. Complementary to the angular line nodes widely present in the literature, the C ∞ v symmetry here allows radial line nodes (RLNs) due to the nonlinear momentum dependence in the OPs. The topology of the RLNs in the mixed case shows a distinctly different characterization than the half-spin quantum vortex at the Dirac point. We apply this NCS physics to the inversion symmetry broken exciton condensates (ECs) in double quantum wells where the point and the RLNs can be found. On the other hand, for a pure triplet condensate, two fully gapped and topologically distinct regimes exist, separated by a QSHI-like zero energy superconducting state with even number of Majorana modes. We also remark on how the point and the RLNs can be manipulated, enabling an external control on the topology. [ABSTRACT FROM AUTHOR]

We propose in theory a curved nanowire structure that can both serve as a spin inverter and a spin polarizer driven by a periodic Rashba spin–orbit coupling (SOC) and a uniform Dresselhaus SOC. The curved section of the U-shaped quasi-one dimensional nanowire with an arc of radius R and circumferential length π R is divided into segments of equal length initially having only its inherent homogeneous Dresselhaus SOC. Then a Rashba-type SOC is applied at every alternating segment. By tuning the Rashba SOC strength and the incident electron energy, this device can flip the spin at the output of an incoming spin-polarized electron. On the other hand, this same device acts as a spin filter for an unpolarized input for which an outgoing electron with a non-zero polarization can be achieved without the application of an external magnetic field. Moreover, the potential modulation caused by the periodic Rashba SOC enables this device to function as an attenuator for a certain range of incident electron energies that can make the probability current density drop to 10 −4 of its otherwise magnitude in other regimes. [ABSTRACT FROM AUTHOR]

We investigate the electrical control of the spin–orbit (SO) interaction in GaAs wells, involving both one- and two-subband electron occupations altered by a gate potential V g , over a wide range of well widths w 's. Through the self-consistent Schrödinger–Poisson calculation, we determine all the intrasubband Rashba α ν ( ν = 1 , 2 ) and Dresselhaus β ν , and also the intersubband Rashba η and Dresselhaus Γ couplings. We observe two distinct regimes marked off around w = w c = 30 − 35 nm . In the first regime with w < w c , we find the usual behavior of SO couplings, i.e., the intrasubband Rashba couplings α 1 and α 2 have the same sign and both change almost linearly with V g , while the Dresselhaus couplings β 1 and β 2 obeying the relation β 1 < β 2 are almost constant. In contrast, in the second regime with w > w c , we observe that α 1 and α 2 can either have the same sign or opposite signs depending on V g . In addition, even though α 1 sensitively depends on V g , we find that α 2 remains essentially constant within a certain gate voltage range. As for the Dresselhaus couplings in this second regime, the inequality β 1 < β 2 (valid in the first regime) only holds near the symmetric configuration of our wells, but otherwise the inequality tends to be reversed. On the other hand, we find that both the intersubband Rashba η and Dresselhaus Γ couplings change almost linearly with V g in the first regime while in the second one a maximum of | η | occurs near the symmetric configuration. We also determined the persistent-spin-helix symmetry points of the two subbands, where the Rashba and the renormalized (due to cubic corrections) Dressehaus couplings are matched. We find that the helix symmetry for the second subband retains over a broad range of V g 's, thus possibly facilitating its locking in practice. Our results should be essential for experiments pursuing an universal electrical control of the SO interaction in semiconductor nanostructures. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR) parameters ( g factors g∥, g⊥ and hyperfine structure constants A∥, A⊥) and the local structure of the tetragonal Cu2+ center in trigonal ZnSeF6·6H2O crystal are theoretically investigated from the perturbation formulas of these parameters for a 3d9 ion in tetragonally elongated octahedra. In the calculated formulas, the contributions to the EPR parameters from ligand orbital and spin-orbit coupling are included on the basis of the cluster approach in view of moderate covalency of the studied systems, the required crystal-field parameters are estimated from the superposition model, which enables correlation of the crystal-field parameters and hence the EPR parameters with the tetragonal distortion of the studied [Cu(H2O)6]2+ cluster. According to the calculations, the ligand octahedra around Cu2+ are suggested to suffer relative elongation τ (≈ 0.085 Å) along the [001] (or C4) axis for the tetragonal Cu2+ centers in ZnSeF6·6H2O crystal, due to the Jahn-Teller effect. The results are discussed. [ABSTRACT FROM AUTHOR]

We investigate the spin–orbit coupling (SOC) effects on the electronic structures and semi-classic transport coefficients of half-Heusler ANiB (A = Ti, Hf, Sc, Y; B Sn, Sb, Bi) by using generalized gradient approximation (GGA). Calculated results show that SOC splits the valence bands at high symmetry Γ point, and modifies the outline of Γ-centered valence bands, which has remarkable effects on the electron transport properties. Thermoelectric properties are performed through solving Boltzmann transport equations within the constant scattering time approximation. It is found that the compounds containing Sn atom have larger power factor in p-type doping than ones in n-type doping, and it is just the opposite for compounds containing Sb and Bi elements. The SOC has obvious detrimental influence on power factor in p-type doping, while has a negligible effect in n-type doping. These can be understood by considering the effects of SOC on the valence bands and conduction bands. The maximum power factors (MPF) are extracted in n-type and p-type doping with GGA and GGA + SOC, and the MPF at 300 K with SOC is predicted to be about 4.25%∼ 44.13% smaller than that without SOC in the case of p-type doping for ANiB (A = Ti, Hf, Sc, Y; B Sn, Sb, Bi). Therefore, it is crucial to consider SOC effects for theoretical analysis in the case of p-type doping in half-Heusler compounds composed of heavy elements. [ABSTRACT FROM AUTHOR]

Polarized absorption spectra and magnetic circular dichroism (MCD) spectra of Nd 0.5 Gd 0.5 Fe 3 (BO 3 ) 4 single crystal were measured in the range of 10000–21000 cm −1 and at temperatures 2–300 K. On the basis of these data, in the paramagnetic state of the crystal, the 4 f states of the Nd 3+ ion were identified in terms of the irreducible representations and in terms of | J , ± M J 〉 wave functions of the free atom. The changes of the Landé factor during f–f transitions were found theoretically in the | J , ± M J 〉 wave functions approximation and were determined experimentally with the help of the measured MCD spectra. In the majority of cases the experimentally found values are close to the theoretically predicted ones. [ABSTRACT FROM AUTHOR]

The present study gives experimental evidence of two-dimensional electronic states localized in subsurface layers of a Ge(1 1 1) substrate, in which a monolayer of Pb adsorbed on a Ge(1 1 1) surface is used as a template. We observed three pairs of the subsurface states by angle-resolved photoelectron spectroscopy, which are closely related to bulk heavy-hole, light-hole and spin–orbit split-off bands of Ge(1 1 1). The heavy-hole- and light-hole-derived bands show the Rashba-type band crossing at the Γ ¯ point. A density functional theory calculation suggests that the branches of these bands exhibit the Rashba-type spin splitting. On the other hand, we observed peculiar spin polarization for the subsurface states attributed to the bulk spin–orbit split-off band by spin- and angle-resolved photoelectron spectroscopy, where spin polarization of each branch is inverted with respect to Γ ¯ and the degeneracy, expected for a normal Rashba spin-split surface state is lifted at Γ ¯ . [ABSTRACT FROM AUTHOR]

The surface of W(1 1 0) exhibits a flattened Dirac-cone-like surface state S 1 with a remarkable spin texture within a spin–orbit-induced symmetry gap. Along Γ S ¯ , S 1 hybridizes spin-selectively with an almost spin-degenerate surface state S 2 . Beyond the spin-selective hybridization point, the surface state S 2 exhibits a spin splitting with a change of the spin polarization at the band bottom. For normal electron emission, S 1 shows spin-dependent intensities depending on the experimental geometry. This behavior is understood as a consequence of a mixed Σ 1 and Σ 3 symmetry of the state. This finding opens a new pathway to studies of the orbital symmetry of electronic states in solids with spin–orbit interaction, without the need of polarization-dependent ARPES. [ABSTRACT FROM AUTHOR]

Topological semimetals may have substantial applications in electronics, spintronics, and quantum computation. Recently, ZrTe was predicted as a new type of topological semimetal due to the coexistence of Weyl fermions and massless triply degenerate nodal points. In this work, the elastic and transport properties of ZrTe are investigated by combining the first-principles calculations and semiclassical Boltzmann transport theory. Calculated elastic constants prove the mechanical stability of ZrTe, and the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio also are calculated. It is found that spin–orbit coupling (SOC) has slightly enhanced effects on the Seebeck coefficient, which along the a(b) and c directions for pristine ZrTe at 300 K is 46.26 μ VK ^−1 and 80.20 μ VK ^−1 , respectively. By comparing the experimental electrical conductivity of ZrTe (300 K) with the calculated value, the scattering time is determined as 1.59 × 10 ^−14 s. The predicted room-temperature electronic thermal conductivity along the a(b) and c directions is 2.37 ${\mathrm{Wm}}^{-1}{{\rm{K}}}^{-1}$ and 2.90 ${\mathrm{Wm}}^{-1}{{\rm{K}}}^{-1}$ , respectively. The room-temperature lattice thermal conductivity is predicted as 17.56 ${\mathrm{Wm}}^{-1}{{\rm{K}}}^{-1}$ and 43.08 ${\mathrm{Wm}}^{-1}{{\rm{K}}}^{-1}$ along the a(b) and c directions, showing very strong anisotropy. Calculated results show that isotope scattering produces an observable effect on lattice thermal conductivity. To observably reduce lattice thermal conductivity by nanostructures, the characteristic length should be smaller than 70 nm, based on cumulative lattice thermal conductivity with respect to the phonon mean free path (MFP) at 300 K. It is noted that the average room-temperature lattice thermal conductivity of ZrTe is slightly higher than that of isostructural MoP, which is due to larger phonon lifetimes and smaller Grüneisen parameters. Finally, the total thermal conductivity as a function of temperature is predicted for pristine ZrTe. Our works provide valuable information for ZrTe-based nano-electronics devices, and motivate further experimental works to study elastic and transport properties of ZrTe.

We investigate a tight-binding model on a two-dimensional square lattice with three terms: the Rashba spin-orbit coupling, the real amplitude next-nearest spin-orbit coupling, and an exchange field. We calculate the first Chern number to identify band topology. It is found that the Chern number takes the quantized values of C1 = 1, 2 and the chiral edge modes can be obtained. Therefore our model realizes the quantum anomalous Hall (QAH) effect. The Rashba coupling is positive for the QAH phase while the next-nearest coupling is detrimental to it. By increasing the exchange field intensity, the Chern number changes from quantized value 2 to 0. The behavior of the edge states is also studied. Particularly for C1 = 2 case, there are two gapless spin-polarized edge states with the same spin polarization moving in the same spatial direction. This indicates that their appearance is topological rather than accidental. [ABSTRACT FROM AUTHOR]

The topological order of single-crystal Bi and its surface states on the (111) surface are studied in detail based on empirical tight-binding (TB) calculations. New TB parameters are presented that are used to calculate the surface states of semi-infinite single-crystal Bi(111), which agree with the experimental angle-resolved photoelectron spectroscopy results. The influence of the crystal lattice distortion is surveyed and it is revealed that a topological phase transition is driven by in-plane expansion with topologically non-trivial bulk bands. In contrast with the semi-infinite system, the surface-state dispersions on finite-thickness slabs are non-trivial irrespective of the bulk topological order. The role of the interaction between the top and bottom surfaces in the slab is systematically studied, and it is revealed that a very thick slab is required to properly obtain the bulk topological order of Bi from the (111) surface state: above 150 biatomic layers in this case.

Four specimens of two compositions of the spinel oxide system CuAlCrFeO with x = 0.2 and 0.6 have been synthesized by double sintering ceramic technique with different thermal history i.e. quenched and slow-cooled. X-ray diffractometry has confirmed that tetragonal distortion is present in slow-cooled sample, while it is absent in quenched sample. The lower value of saturation moment compared to Neel's moment for each composition is explained by invoking random canting of spins model. Hyperfine interaction parameters: nuclear hyperfine field, quadrupole splitting (shifts), isomer shift and Fe ion distribution are deduced through computer simulation of Mössbauer spectra. Fe Mössbauer spectra recorded at room temperature show the effect of magnetic dilution of inter-sublattice ( A- B) interaction (frustration) more in case of quenched-sample compared to slow-cooled one. FTIR spectra also corroborate the influence of Jahn-Teller (J-T) distortion of octahedral void arising due to larger Cu ion occupancy at octahedral sites. The force constants are also estimated from FTIR spectra. [ABSTRACT FROM AUTHOR]

Based on the transfer-matrix method, the charge transport properties of the electrons through a ballistic graphene-based quantum tunneling junctions with the inhomogeneous spin-orbit interactions (SOIs) have been investigated theoretically. In sharp contrast to the conventional normal metal/2D electron gas/normal metal junctions and the graphene-based double junctions with a big incident energy, the normal transmission coefficient monotonically decreases with the length of middle region in the limit of a vanishing Rashba SOI term. While only the Rashba SOI exists, the maximum of the sum of the transmission coefficient equates to about 0.5, only one half of the value for the case of a big incident energy. It is also found that the conductance can be dominated by the incident energy and the SOI strength. It is anticipated to apply such a phenomenon to design the spin-polarized electron devices based on the graphene materials. [ABSTRACT FROM AUTHOR]

It has been found that the energy of the transitions of acceptors to resonance states under a spin-split valence subband depends on the isotope content of the silicon matrix. An estimate of the isotope effect for the spin-orbit splitting of the valence band of silicon has been obtained. [ABSTRACT FROM AUTHOR]

Magnetooptical studies of heterostructures with type-II InSb quantum dots in the InAs matrix grown by molecular beam epitaxy are carried out. Unusual behavior of magnetophotoluminescence from quantum dots measured in the Faraday geometry in the samples with multiple planes of quantum dots is found. Specifically, the peak with σ− polarization, which corresponds to transitions of electrons with s = +1/2, has a higher energy than the σ+ peak corresponding to s = −1/2, which contradicts the negative value of the electron g factor both in the InAs matrix and in the InSb quantum dot. The effect can be interpreted as the result of competition of two channels of radiative recombination, which differ by the initial states of electrons belonging either to the InSb quantum dots or to shallow-level donors in the InAs matrix. [ABSTRACT FROM AUTHOR]

An explicit analytic expression is derived for the magnetic moment of a 2D electron gas taking into account the spin-orbit interaction in the Rashba model with T = 0. The cases of constant chemical potential and number of electrons are investigated. The magnetic field and temperature dependences of the magnetic moment are analyzed. The results are compared with the results of experimental studies of magnetization. [ABSTRACT FROM AUTHOR]

By angle-resolved photoemission the electronic structure of quantum films of Mg, Ag, and Au has been compared on W(110) and Mo(110) substrates which are structurally and electronically very similar but differ in atomic number. In all cases, substrate-induced states with characteristic dispersions are observed in the region of a bulk band gap of the substrate. Based on the comparison between Mo and W, we can exclude that previously observed Mg states are spin-orbit split but observe a spin-orbit splitting in Ag and Au monolayers. This splitting is mainly caused by the substrate because it does not differ much between Ag and Au overlayers despite the large difference in atomic number. [ABSTRACT FROM AUTHOR]

Spin relaxation in the impurity band of a 2D semiconductor with spin-split spectrum and hyperfine interaction in the external magnetic field is considered. Two contributions to the spin relaxation are shown to be relevant: the one given by optimal impurity configurations with the hop-waiting time inversely proportional to the external magnetic field and another one related to electron motion over large distances. The average spin relaxation rate is calculated. [ABSTRACT FROM AUTHOR]

Absorption of linearly polarized electromagnetic radiation by a two-dimensional electron gas in a lateral-superlattice structure subjected to a perpendicular magnetic field is calculated analytically and numerically for the first time, taking into account Rashba’s spin-orbit coupling and Zeeman splitting. Calculations are carried out for semiconductor heterostructures characterized by weak and sufficiently strong spin-orbit coupling (AlGaAs/GaAs and GaAs/InGaAs, respectively). The nature of the new effect related to intense magnetoabsorption of electromagnetic radiation in the submillimeter range by a two-dimensional electron gas in a superlattice with strong spin-orbit coupling is analyzed. Magneto-optical experiments aimed at studying spin-Peierls states of charge carriers are discussed and, in this context, optimum parameters for semiconductor structures with spin-orbit coupling and values of the magnetic field are determined. [ABSTRACT FROM AUTHOR]

Polarized excited state absorption spectra of Er, Yb:YAB are reported. The Stark levels of the 4I15/2, 4I13/2, and 4I11/2 multiplets of Er3+ have been derived from the measured low-temperature absorption and fluorescence spectra. The stimulated emission spectra have been calculated using the reciprocity method, and the radiative lifetime of the erbium 4I13/2 level has been determined indicating high nonradiative decay rates. The thermal conductivity of Er-Yb-codoped YAB crystals has been measured. [ABSTRACT FROM AUTHOR]

The anomalous Hall effect and spin Hall effect originate due to spin-orbit coupling that in the Kohn-Luttinger k · p formalism is represented by anomalous terms in the coordinate and velocity operators. Relation of these operators to the Berry curvature in the momentum space is presented for electrons in GaAs type semiconductors. For centrosymmetric semiconductors, transformational properties of Berry curvature are discussed. [ABSTRACT FROM AUTHOR]

We analyze the spin-orbit terms in multi-subband quasi-two-dimensional electron systems, and how they descend from the bulk Hamiltonian of the conduction band. Measurements of spin-orbit terms in one subband alone are shown to give incomplete information on the spin-orbit Hamiltonian of the system. They should be complemented by measurements of inter-subband spin-orbit matrix elements. Tuning electron energy levels with a quantizing magnetic field is proposed as an experimental approach to this problem. [ABSTRACT FROM AUTHOR]

The effect of a magnetic field on the energy gap of the charge density wave (CDW) in NbSe3 near the temperature T p2 of the lower Peierls transition has been investigated using interlayer tunneling spectroscopy. It has been shown that the magnetic field increases the energy gap and can even induce it at temperatures higher than T p2 by 15–20 K. As the field strength increases, the peak amplitude of the gap singularity of the tunneling spectrum first increases, reaches its maximum at 20–30 T, and then decreases. The increase in the gap peak amplitude is attributed to the field-induced improvement of the condition of the CDW nesting, while the decrease in the amplitude in high fields, to the breakdown of the ground state caused by its Zeeman splitting. [ABSTRACT FROM AUTHOR]

Different types of quantum beats were experimentally observed in the photoluminescence kinetics of semiconductor nanostructures with InP quantum dots characterized by strong inhomogeneous broadening of the optical transitions. Specific types of beats were selected by varying the magnitude and orientation of the magnetic field, the applied bias voltage, and the frequencies of the exciting and detected light. Parameters of the fine structure of electrons and holes in the system under study and characteristic relaxation times of the spin coherence are determined from the experimental data. [ABSTRACT FROM AUTHOR]

In studying circular-polarized photoluminescence, a high degree of spin orientation of electrons is observed in the n-type region of an InAs-based diode structure in a magnetic field in the Faraday geometric lay-out of the experiment. The degree of polarization is as high as 90% in the field of 2 T. In contrast, the degree of polarization in conventional InAs layers without a p-n junction is not higher than 20% in fields as high as 4 T. This effect is attributed to the built-in field of the p-n junction: the built-in field prevents localization of non-equilibrium electrons at shallow donor centers and, thus, allows orientation of electron spins due to Zeeman splitting in the conduction band. [ABSTRACT FROM AUTHOR]

We discuss a model nonfrustrated magnetoelectric in which a sufficiently strong magnetoelectric coupling produces an incommensurate magnetic order leading to ferroelectricity. Properties of the magnetoelectric in the magnetic field directed perpendicular to the wave vector describing the spin helix are considered in detail. Analysis of the classical energy shows that in contrast to the naive expectation, the onset of ferroelectricity occurs at a field H c1 that is lower than the saturation field H c2. We have H c1 = H c2 at large enough magnetoelectric coupling. We show that at H = 0, ferroelectricity occurs at T = T FE < T N. A qualitative discussion of the phase diagram in the H-T plane is presented within the mean-field approach. [ABSTRACT FROM AUTHOR]

Spin relaxation is studied in the hopping conduction mode in 2D arrays of quantum dots (QDs) with structural asymmetry. It is shown that the absence of the “up-down” symmetry in a QD leads to the emergence of a new spin relaxation mechanism in tunneling in a 2D QD array. The difference in spin relaxation mechanisms for symmetric and asymmetric QDs is demonstrated on the basis of theoretical analysis of an elementary event (jump between two tunnel-coupled dots). It is shown that spin flip during tunneling between QDs is the main spin relaxation mechanism in the transport in dense arrays of QDs in Ge placed in weak (1–10 T) magnetic fields. [ABSTRACT FROM AUTHOR]

We reconsider the conventional Moriya approach to the Dzyaloshinsky-Moriya antisymmetric exchange coupling for a single Cu1-O-Cu2 bond in cuprates using a perturbation scheme that provides an optimal way to account for intra-atomic electron correlations, low-symmetry crystal field, and local spin-orbital contributions with a focus on the oxygen term. The Dzyaloshinsky vector and the corresponding weak ferromagnetic moment are shown to be a superposition of comparable and, sometimes, competing local Cu and O contributions. We predict the effect of oxygen staggered spin polarization in the antiferromagnetic edge-shared CuO2 chains due to the uncompensated oxygen Dzyaloshinsky vectors. The polarization is perpendicular to both the main chain antiferromagnetic vector and the CuO2 chain normal. The intermediate 17O NMR is shown to be an effective tool to inspect the effects of Dzyaloshinsky-Moriya coupling in an external magnetic field. In particular, we argue that the puzzling planar 17O Knight shift anomalies observed in the paramagnetic phase of the generic Dzyaloshinsky-Moriya antiferromagnetic cuprate La2CuO4 can be assigned to the effect of the field-induced staggered magnetization. Finally, we revisit the effects of symmetric spin anisotropy, in particular, those directly induced by the Dzyaloshinsky-Moriya coupling. The perturbation scheme generalizes the well-known Moriya approach and presents a basis for reliable quantitative estimates for the symmetric partner of the Dzyaloshinsky-Moriya coupling. In contrast to the conventional standpoint, the parameters of the effective two-ion spin anisotropy are shown to incorporate the contributions of a single-ion anisotropy for two-hole configurations at both Cu and O sites. [ABSTRACT FROM AUTHOR]

A mechanism of the spin-galvanic effect associated with spin-dependent scattering is proposed. The electrical current in a system of spin-polarized two-dimensional carriers is induced due to interference of spin-preserving scattering processes and spin relaxation processes. The spin-galvanic effect is studied for heterostructures with the Elliott-Yafet and Dyakonov-Perel spin relaxation mechanisms. The proposed contribution to the spin-galvanic current may be dominant in A3B5 asymmetric quantum wells. [ABSTRACT FROM AUTHOR]

The electroluminescence and photoluminescence of bulk n-InAs with a high concentration of donors ( N d ≈ 5 × 1016 cm−3) is studied experimentally in magnetic field in the Faraday layout of the experiment. Under the conditions of electrical injection, the photon energy corresponding to the electroluminescence peak exceeds the energy band gap E g. When a magnetic field is applied, the energy of the peak becomes lower than E g, and the peak splits into two circular-polarized components. The splitting depends on the injection current. In moderate magnetic fields (about 2 T), the splitting can be much more profound than the calculated splitting corresponding to the well-known g factor of electrons in InAs. The effect is attributed to different degrees of magnetic freezing-out of electrons with different spin orientation. The maximum in the dependence of the degree of polarization of photoluminescence on the magnetic field and the behavior of the photoluminescence line width support the model suggested. [ABSTRACT FROM AUTHOR]

Spin dynamics in the impurity band of a semiconductor with the spin-split spectrum is considered. Due to the splitting, phonon-assisted hops from one impurity to another axe accompanied by rotation of the electron spin, which leads to spin relaxation. The system is strongly inhomogeneous because of exponential variation of hopping times. However, at very small coupling an electron diffuses over a distance exceeding the characteristic scale of the inhomogeneity during the time of spin relaxation, so one can introduce an averaged spin relaxation rate. At larger values of coupling, the system is effectively divided into two subsystems: one where relaxation is very fast and another where relaxation is rather slow. In this case, spin decays due to the escape of the electrons from one subsystem to another. As a result, the spin dynamics is nonexponential and hardly depends on spin-orbit coupling. [ABSTRACT FROM AUTHOR]

The conductance of a quantum ring has been calculated on the basis of the tunneling Hamiltonian in the quasiballistic regime of the motion of electrons with allowance for the spin-orbit interaction. The effect of the scattering of electrons by a single short-range interacting impurity in the quantum ring on the tunneling electron current is analyzed. Two types of impurities, spinless and paramagnetic, are considered. The conductance symmetry is discussed for various electron-spin orientations with respect to change in the sign of the magnetic flux through the quantum ring. [ABSTRACT FROM AUTHOR]