Electron G-factor Research Articles

The effect of the electron–phonon interaction on the energy levelsand g-factor of electrons in nanowires

We analyze the effect of longitudinal optical phonons on the energy states of electrons in a nanowire in the presence of Rashba interaction and an in-plane magnetic field. Due to the electron–phonon interaction, an energy splitting appears at zero wave vector accompanied by a downward shift of the dispersion relation in the absence of external magnetic fields. The splitting increases linearly with the product of the Rashba parameter and the dimensionless constant characterizing the Fröhlich Hamiltonian. It also induces an enhancement in the [Formula: see text]-factor that is inversely proportional to the strength of the magnetic field. Moreover, we calculate the contribution of Rashba intersubband coupling (RIC) to the electron energy. This contribution does not influence the [Formula: see text]-factor for the case of parallel magnetic field to the nanowire, but it causes reduction in it by increasing the angle between the nanowire and the field.

Giant g-factors and fully spin-polarized states in metamorphic short-period InAsSb/InSb superlattices

Realizing a large Landé g-factor of electrons in solid-state materials has long been thought of as a rewarding task as it can trigger abundant immediate applications in spintronics and quantum computing. Here, by using metamorphic InAsSb/InSb superlattices (SLs), we demonstrate an unprecedented high value of g ≈ 104, twice larger than that in bulk InSb, and fully spin-polarized states at low magnetic fields. In addition, we show that the g-factor can be tuned on demand from 20 to 110 via varying the SL period. The key ingredients of such a wide tunability are the wavefunction mixing and overlap between the electron and hole states, which have drawn little attention in prior studies. Our work not only establishes metamorphic InAsSb/InSb as a promising and competitive material platform for future quantum devices but also provides a new route toward g-factor engineering in semiconductor structures.

Accurate determination of the electron spin polarization in magnetized iron and nickel foils for Møller polarimetry

The Møller polarimeter in Hall A at Jefferson Lab in Newport News, VA, has provided reliable measurements of electron beam polarization for the past two decades. Past experiments have typically required polarimetry at the 1% level of absolute uncertainty which the Møller polarimeter has delivered. However, the upcoming proposed experimental program including MOLLER and SoLID have stringent requirements on beam polarimetry precision at the level of 0.4% (The MOLLER Collaboration, 2014; The SoLID collaboration, 2019), requiring a systematic re-examination of all the contributing uncertainties.Møller polarimetry uses the double polarized scattering asymmetry of a polarized electron beam on a target with polarized atomic electrons. The target is a ferromagnetic material magnetized to align the spins in a given direction. In Hall A, the target is a pure iron foil aligned perpendicular to the beam and magnetized out of plane parallel or antiparallel to the beam direction. The acceptance of the detector is engineered to collect scattered electrons close to 90° in the center of mass frame where the analyzing power is a maximum (-7/9).One of the leading systematic errors comes from determination of the target foil polarization. Polarization of a magnetically saturated target foil requires knowledge of both the saturation magnetization and g′, the electron g-factor which includes components from both spin and orbital angular momentum from which the spin fraction of magnetization is determined. Target foil polarization has been previously addressed in a 1997 publication “A precise target for Møller polarimetry” by de Bever et al. (1997) at a level of precision sufficient for experiments up to this point. Several shortcomings with the previous published value require revisiting the result prior to MOLLER. This paper utilizes the existing world data to provide a best estimate for target polarization for both nickel and iron foils including uncertainties in magnetization, high-field and temperature dependence, and fractional contribution to magnetization from orbital effects. We determine the foil electron spin polarization at 294 K to be 0.08020 ± 0.00018 (@4 T applied field) for iron and 0.018845±0.000053 (@2 T applied field) for nickel. We conclude with a brief discussion of additional systematic uncertainties to Møller polarimetry using this technique.

Relativistic exact two-component coupled-cluster calculations of electronic g-factors for heavy-atom-containing molecules pertinent to search of new physics

Exact two-component (X2C) coupled-cluster calculations of electronic g-factors for heavy-atom-containing small molecules pertinent to search of new physics beyond the standard model (BSM) is reported. A magnetic-field-dependent unitary transformation of the Dirac Hamiltonian has been adopted to enable a simple inclusion of the quantum electrodynamics correction to the free-electron g-factor in the four-component formulation. The X2C transformation is subsequently employed to eliminate the positronic degrees of freedom to enhance computational efficiency without significant loss of accuracy. The relationship of the present scheme to alternative four- and two-component formulations is discussed. To demonstrate the accuracy and usefulness of the present X2C scheme, we report coupled-cluster calculations for electronic g-factors of representative heavy-metal-containing small molecules including those relevant to precision spectroscopic search of BSM physics.

Small Charging Energies and g-Factor Anisotropy in PbTe Quantum Dots

PbTe is a semiconductor with promising properties for topological quantum computing applications. Here, we characterize electron quantum dots in PbTe nanowires selectively grown on InP. Charge stability diagrams at zero magnetic field reveal large even–odd spacing between Coulomb blockade peaks, charging energies below 140 μeV and Kondo peaks in odd Coulomb diamonds. We attribute the large even–odd spacing to the large dielectric constant and small effective electron mass of PbTe. By studying the Zeeman-induced level and Kondo splitting in finite magnetic fields, we extract the electron g-factor as a function of magnetic field direction. We find the g-factor tensor to be highly anisotropic with principal g-factors ranging from 0.9 to 22.4 and to depend on the electronic configuration of the devices. These results indicate strong Rashba spin–orbit interaction in our PbTe quantum dots.

Dual Relativistic Quantum Mechanics I

In \cite{2} it was shown that Einstein's special theory of relativity and Maxwell's field theory have mathematically equivalent dual versions. The dual versions arise from an identity relating observer time to proper time as a contact transformation on configuration space, which leaves phase space invariant. The special theory has a dual version in the sense that, for any set of $n$ particles, every observer has two unique sets of global variables $({\bf{X}}, t)$ and $({\bf{X}}, \tau)$ to describe the dynamics, where ${\bf{X}}$ is the (unique) canonical center of mass. In the $({\bf{X}}, t)$ variables, time is relative and the speed of light is unique, while in the $({\bf{X}}, \tau)$ variables, time is unique and the speed of light is relative with no upper bound. In the Maxwell case, the two sets of particle wave equations are not equivalent. The dual version contains an additional longitudinal (dissipative) radiation term that appears instantaneously with acceleration, leading to the prediction that radiation from a betatron (of any frequency) will not produce photoelectrons. A major outcome is the dual unification of Newtonian mechanics and classical electrodynamics with Einstein's special theory of relativity, without a self-energy divergency, or need of the problematic Lorentz-Dirac equation or any assumptions about the size or structure of a particle. The purpose of this paper is to introduce and develop the dual theory of relativistic quantum mechanics. We obtain three distinct dual relativistic wave equations that reduce to the Schr{\"o}dinger equation when minimal coupling is turned off. We show that the dual Dirac equation provides a new formula for the anomalous magnetic moment of a charged particle. We can obtain the exact value for the electron g-factor and phenomenological values for the muon and proton g-factors.

Electron g-factor determined for quantum dot circuit fabricated from (110)-oriented GaAs quantum well

The choice of substrate orientation for semiconductor quantum dot circuits offers opportunities for tailoring spintronic properties such as g-factors for specific functionality. Here, we demonstrate the operation of a few-electron double quantum dot circuit fabricated from a (110)-oriented GaAs quantum well. We estimate the in-plane electron g-factor from the profile of the enhanced inter-dot tunneling (leakage) current near-zero magnetic field. Spin blockade due to Pauli exclusion can block inter-dot tunneling. However, this blockade becomes inactive due to hyperfine interaction mediated spin flip-flop processes between electron spin states and the nuclear spin of the host material. The g-factor of absolute value ∼0.1 found for a magnetic field parallel to the direction [1¯10] is approximately a factor of four lower than that for comparable circuits fabricated from a material grown on widely employed standard (001) GaAs substrates and is in line with reported values determined by purely optical means for quantum well structures grown on (110) GaAs substrates.

Ultrafast entanglement switching and singlet–triplet transitions control via structured terahertz pulses

Terahertz (THz) vector beams with spatially textured polarization are proposed to steer the spin and spatial distributions of two interacting electrons in a quantum dot. We study theoretically the spatiotemporal evolution of the spin and the charge-current densities and quantify the behavior of entanglement by calculating the concurrence. Both aspects are shown to be controllable efficiently and on the picosecond (ps) time scale by the parameters of the driving fields. Analyzing two different materials, GaAs and InGaAs, with different electron g-factors, we study the relationship between the g-factor and type of spin–orbit coupling required to produce efficient interlevel transitions. The results are useful for applications of quantum dots as basic nanoscale hardware elements in quantum information technology and for producing swiftly the appropriate spin and charge currents on demand.

Electronic structure, effective masses and g-factors and strain induced crystal field splitting of WZ-InP by method

In this work, we study the electronic structure of wurtzite (WZ) InP, following a procedure developed earlier by us for WZ-GaN [(2018) J. Phys. Chem. Solids 112, 280] and WZ-ZnO [(2016) Semicond. Sci. Technol. 31, 035018], where the Hamiltonian was diagonalised by taking the conduction band and one valence band at a time. We consider the effects of other valence bands on a given valence band through second order perturbation theory of the Hamiltonian. Valence band dispersions are compared with previous calculations. We notice satisfactory agreement between our results and the previous one. Valence band effective masses are calculated from the valence band dispersions and conduction band effective masses were calculated from standard effective mass formulas. While valence band effective masses compare well with earlier calculations the transverse electronic effective mass is slightly higher compared to the experimental value and other reported values. However, when we use a different set of momentum matrix elements the transverse effective mass agrees well with the experimental value but the longitudinal value becomes slightly less than the experimental value. Thus the calculations are quite sensitive to the change in momentum matrix elements. Additionally, we calculate the effective masses as functions of the wave vector along and Our results for the g-factors are the first of its kind for WZ-InP. These results are quite sensitive to the change of sign of the spin–orbit parameters. The changes are not significant in case of electronic g-factors. But these are quite significant for the transverse valence band effective g-factors. Even change of sign is noticed. Spin–orbit mixing is found to be important and responsible for the observed anisotropy. Electronic g-factors agree well with reported experimental values. We also study the effect of strain on the crystal field splitting energy at the point. Trends obtained as functions of strain match with a previous calculation.

Inertial and gravitational effects on a geonium atom

We reveal all linear order inertial and gravitational effects on a non-relativistic Dirac particle (mass m) on the Earth up to the order of 1/m in the Foldy–Wouthuysen-like expansion. Applying the result to Penning trap experiments where a Dirac particle experiences the cyclotron motion and the spin precession in a cavity, i.e. a geonium atom, we study modifications to the g-factor of such as the electron. It is shown that each correction from gravity has different dependence on the cyclotron frequency and the mass m. Therefore, their magnitude change depending on situations. In a particular case of an electron g-factor measurement, the dominant correction to the observed g-factor comes from effects of the Earth’s rotation, which is δg/2 ≃ 5.2 × 10−17. It may be detectable in the near future.

Phonon-assisted relaxation between triplet and singlet states in a self-assembled double quantum dot

We study theoretically phonon-induced spin dynamics of two electrons confined in a self-assembled double quantum dot. We calculate the transition rates and time evolution of occupations for the spin-triplet and spin-singlet states. We characterize the relative importance of various relaxation channels, including two-phonon processes, as a function of the electric and magnetic fields. The simulations are based on a model combining the eight-band varvec{k}!cdot !varvec{p} method and configuration-interaction approach. We show that the electron g-factor mismatch between the Zeeman doublets localized on different dots opens a relatively fast triplet-singlet phonon-assisted relaxation channel. We also demonstrate, that the relaxation near the triplet-singlet anticrossing is slowed down up to several orders of magnitude due to vanishing of some relaxation channels.

Complete polarization of electronic spins in OLEDs

At low temperatures and high magnetic fields, electron and hole spins in an organic light-emitting diode become polarized so that recombination preferentially forms molecular triplet excited-state species. For low device currents, magnetoelectroluminescence perfectly follows Boltzmann activation, implying a virtually complete polarization outcome. As the current increases, the magnetoelectroluminescence effect is reduced because spin polarization is suppressed by the reduction in carrier residence time within the device. Under these conditions, an additional field-dependent process affecting the spin-dependent recombination emerges, possibly related to the build-up of triplet excitons and their interaction with free charge carriers. Suppression of the EL alone does not prove electronic spin polarization. We therefore probe changes in the spin statistics of recombination directly in a dual singlet-triplet emitting material, which shows a concomitant rise in phosphorescence intensity as fluorescence is suppressed. Finite spin-orbit coupling in these materials gives rise to a microscopic distribution in effective g-factors of electrons and holes, Δg, i.e., a distribution in Larmor frequencies. This Δg effect in the pair, which mixes singlet and triplet, further suppresses singlet-exciton formation at high fields in addition to thermal spin polarization of the individual carriers.

Spin Interpreted as the Angular Momentum Curvature, Electron g-factor Interpreted as the Ratio of Toroidal Torsion and Curvature, Unlocking of the Fixed Planck Constant h – New Tests for Old Physics

We have proposed several new rules for the description of events in the microworld. We have newly defined the interpretation of the quantum spin as the angular momentum curvature and defined the geometry of helixes and toroidal helixes of quantum particles. Some new properties of quantum particles can be experimentally tested. Based on this concept we have defined the electron g-factor as the ratio of the toroidal torsion and curvature and events between the electron and its coupling photon. From this model we have extracted the values of the fine-structure constant α and the Planck constant h. The comparison of these values with the latest experimental data reveals some possible circular arguments in the experimental determination – the so-called SI barrier created by the fixing of the SI constants (SI – International System of Units). We propose on the one side to analyze those possible circular arguments and on the other side to continue to develop new generations of instruments for getting one or two more significant figures of those values h and c. The predictions of this classical model could be compared with the best predictions of QED (quantum electrodynamics) for the fine-structure constant α.

Effective mass of heavy, light, and spin split-off band electron and hole g-factor in cubic perovskite materials

Analytical expressions for the effective mass of heavy, light, and spin split-off electrons are obtained by diagonalizing the k⋅p Hamiltonian for cubic perovskite crystal structures and used to calculate these in nine perovskite materials. An expression for the effective hole g-factor is also derived and calculated in these perovskites. The calculated effective mass of heavy electrons ranges from 1.619 m0 to 0.201 m0, of light electrons from 0.357 m0 to 0.146 m0, and of spin split-off electrons from 0.584 m0 to 0.169 m0. It is found that Cl- and Pb-based perovskite materials have larger heavy, light, and spin split-off electron effective masses. It is also found that the effective g-factor increases with the atomic size, from Cl to I, for the series CsSnX3(X=Cl,Br,I).

Electron g-factor in nanostructures: continuum media and atomistic approach

We report studies of {varvec{k}}-dependent Landé g-factor, performed by both continuous media approximation {varvec{k}}{varvec{cdot }}{varvec{p}} method, and atomistic tight-binding hbox {sp}^3hbox {d}^5hbox {s}^* approach. We propose an effective, mesoscopic model for InAs that we are able to successfully compare with atomistic calculations, for both very small and very large nanostructures, with a number of atoms reaching over 60 million. Finally, for nanostructure dimensions corresponding to near-zero g-factor we report electron spin states anti-crossing as a function of system size, despite no shape-anisotropy nor strain effects included, and merely due to breaking of atomistic symmetry of cation/anion planes constituting the system.

Особенности поведения ионов Mn-=SUP=-2+-=/SUP=- в 3D-дираковском полуметалле alpha-Cd-=SUB=-3-=/SUB=-As-=SUB=-2-=/SUB=- по данным ЭПР

The behavior of the manganese impurity in the 3D Dirac semimetal Cd3As2 has been studied by EPR and electromagnetic measurements. It was found that, in contrast to doping with europium, doping with manganese, as well as with iron, does not lead to a change in the sign of the magnetoresistance, which is almost completely suppressed at high manganese concentrations. In this case, a change in the type of the influence of the magnetic field on the contact potential is manifested. The g-factors measured in EPR coincide with the g-factor of a free electron at all temperatures, which, taking into account the fluctuation behavior of the EPR linewidth and the reduced magnetic moment on Mn2 +, indicates the formation of short-lived bound states of the Mn2 + ion and conduction electrons - antiferromagnetic polarons.

Spin-orbit interaction in AlAs quantum wells

Abstract The spin-orbit coupling was investigated in a series of AlAs quantum wells with different width containing high quality two dimensional electron systems. The interaction between the spin degree of freedom and the orbital motion of the electrons in the regime of the integer quantum Hall effect induced the filling factor dependent renormalization of the electron g-factor. Such g-factor modification probed by electron spin resonance was well resolved in all of the samples studied in a wide range of magnetic fields. Theoretical analysis of this phenomenon allowed us to identify the Dresselhaus-like spin-orbit interaction as the dominant term and to measure its strength β. The value of β turned out to depend rather weakly on the quantum well width, yet such a behavior agrees well with the theoretical calculations. The bulk Dresselhaus constant extracted from the fit turned out to be 3.5 eV × A3.

EPR Spectroscopy of Diazoquinone–Novolac Resist Films Implanted with P+ and B+ Ions

The nature of stable radicals in FP9120 positive photoresist films implanted with boron and phosphorus ions and deposited on the surface of single-crystal silicon wafers has been determined using the EPR technique. At an implantation fluence of 6 × 1015 cm−2, a narrow singlet isotropic line with a g-factor of 2.0064 is observed in the EPR spectrum. As the fluence increased to 1.2 × 1016 cm−2, the g-factor decreased to values close to the g-factor of the free electron. The concentration of paramagnetic centers was higher during implantation of phosphorus ions than in the samples implanted with boron ions. This difference is due to a smaller contribution of nuclear stopping during B+ implantation, which does not exceed 10–15% of electronic stopping. The formation of long-lived paramagnetic centers recorded by EPR a week after implantation of positive phenol–formaldehyde photoresist is due to the presence of a powerful system of conjugated >C=O and –C=C– multiple bonds in the structure of the radicals.

Effects of strain on the [formula omitted] electronic structure and related properties of w-GaN

We consider effects of strain on the k→⋅π→ electronic structure by modifying non-strain k→⋅π→ theory in the presence of uniaxial/biaxial stress and hydrostatic pressure. Here π→ is the relativistic momentum operator and k→ is the wave vector of an electron. The theory is applied to w-GaN. Starting from a non-relativistic electronic Hamiltonian, we show the changes brought about by strain in the position operator, momentum operator and the periodic potential. We extend it to the relativistic Hamiltonian, and then to the k→⋅π→ theory. We modify the k→⋅π→ electronic structure of non-strained w-GaN, previously developed by one of the authors, by incorporating the strain effects on the Luttinger-Kohn parameters. Effect of strain is considered on the Γ-point conduction and valence band energies. Inter-band transition energies are also calculated. We study strained valence band dispersions. Our results agree with previous calculations wherever such calculations exist. Discrepancies, if any, are addressed. We also consider the effect of strain on the effective mass and g-factors of both electrons and holes, in view of their importance in transport and other properties and spintronics. Effective mass results compare well other available calculations. Results for the g-factors are new and show interesting trends.

Electron g -factor engineering for nonreciprocal spin photonics

We study the interplay of electron and photon spin in non-reciprocal materials. Traditionally, the primary mechanism to design non-reciprocal photonic devices has been magnetic fields in conjunction with magnetic oxides, such as iron garnets. In this work, we present an alternative paradigm that allows tunability and reconfigurability of the non-reciprocity through spintronic approaches. The proposed design uses the high-spin-orbit coupling of a narrow-band gap semiconductor (InSb) with ferromagnetic dopants. A combination of the intrinsic and a gate-applied electric field gives rise to a strong external Rashba spin-orbit coupling (RSOC) in a magnetically doped InSb film. The RSOC which is gate alterable is shown to adjust the magnetic permeability tensor via the electron g-factor of the medium. We use electronic band structure calculations (k$\cdot$p theory) to show the gate-adjustable RSOC manifest itself in the non-reciprocal coefficient of photon fields via shifts in the Kerr and Faraday rotations. In addition, we show that photon spin properties of dipolar emitters placed in the vicinity of a non-reciprocal electromagnetic environment is distinct from reciprocal counterparts. The Purcell factor (F$_{p}$) of a spin-polarized emitter (right-handed circular dipole) is significantly enhanced due to a larger g-factor while a left-handed dipole remains essentially unaffected. Our work can lead to electron spin controlled reconfigurable non-reciprocal photonic devices.