Spin-orbit Interaction Parameter Research Articles

Weak Localization and Antilocalization in the Two-Dimensional Electron System on p-Type InAs

We have performed low temperature magnetoresistance measurements of the two-dimensional electron system (2DES) in an inversion layer on p-type InAs. In high magnetic fields perpendicular to the 2DES beating patterns in Shubnikov-de Haas oscillations are observed from which the Rashba spin-orbit interaction parameter is determined. In the low-field regime we perceive weak localization and antilocalization. By fitting to the gathered localization data the elastic, inelastic, and spin relaxation times as well as coherence lengths for diffusive transport are determined for different applied gate-voltages. The Rashba parameter determined from these relaxation times is compared to the values obtained from the high-field Shubnikov-de Haas oscillations.

Spin splitting in modulation-doped AlGaN/GaN two-dimensional electron gas

AlGaN/GaN heterostructure devices have recently been attracting much attention because of their potential for high-performance microwave applications. Therefore, the electronic properties of a two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures have recently been discussed. We studied the magnetoresistance oscillation of the 2DEG at 0.4 K for various backgate voltages, and observed multiple oscillations resulting from spin splitting. The magnetoresistance shows clear beating due to the superposition of three oscillations. The frequency interval between the first and second largest frequencies is proportional to the total electron concentration and the measured spin-orbit interaction parameter agrees with the theoretical one. Therefore, the first and second largest frequencies are found to correspond to spin splitting by the spin-orbit interaction.

Study for realization of spin-polarized field effect transistor in In 0.75Ga 0.25As/In 0.75Al 0.25As heterostructure

For realization of the spin-polarized field effect transistor (spin-FET), we investigated a gated modulation of spin–orbit interaction and a spin-injection from a ferromagnetic metal (FM) to a two-dimensional electron gas (2DEG). Prepared samples were an In 0.75Ga 0.25As/In 0.75Al 0.25As modulation-doped narrow-gap heterojunction grown by molecular beam epitaxy (MBE). For the determination of spin–orbit interaction parameter, α, we measured Shubnikov–de Haas (SdH) oscillations at 1.5 K . We confirmed a modulation of α when a gate voltage was applied. We also carried out spin-injection experiments using a multi-terminal geometry sample, which had two different widths Ni 40Fe 60 electrodes. We observed a spin-valve like effect in a source-drain resistance of ∼0.1% as well as a resistance hysteresis behavior of ∼12% in non-local geometry below 20 K . These results are the first step to realize an active spintronic device, such as spin-FET.

An investigation of tunable spin–orbit interactions in front-gated In 0.75Ga 0.25As/In 0.75Al 0.25As heterojunctions

We investigated zero-field spin-splitting in normal-type In 0.75Ga 0.25As/In 0.75Al 0.25As heterostructure by magnetoresistance measurements at 1.5 K . The maximum value of spin–orbit interaction parameter, α zero, obtained here is 32×10 −12 eVm . We also confirmed a tuning of α zero by applying gate biases. On the other hand, we observed no beat oscillation when the In 0.75Ga 0.25As well width decreased from 30 to 10 nm . These results suggested that interface contribution related to the asymmetry of wave function penetration into the barriers could be enhanced in our heterojunction.

Experimental studies of the NaK 1 3Δ state

The NaK 1 3Δ state has been studied by the perturbation-facilitated optical–optical double resonance technique. Mixed singlet–triplet levels, A(2)1Σ+(vA,J)∼b(1)3Π(vb,J), were pumped from thermally populated rovibrational levels of the ground state, X(1)1Σ+(vX,J±1), using a single-mode cw dye laser. A single-mode cw Ti:Sapphire laser was then used to further excite the NaK molecules to various 1 3Δ(vΔ,NΔ,JΔ) rovibrational levels which were detected by observing collision-induced Λ3→a(1)3Σ+ fluorescence in the green part of the spectrum. The measured energies of the 1 3Δ(vΔ,NΔ) levels were fit to a Dunham expansion, and the Dunham coefficients were used to construct the RKR potential curve. Absolute numbering of the 1 3Δ state vibrational levels was established by a comparison of experimental and calculated 1 3Δ(vΔ,NΔ,JΔ)←b(1)3Π(vb,Jb) absorption line strengths. A deperturbation program was used to determine the vibration-dependent 1 3Δ state spin–orbit interaction parameter. Hyperfine structure of the 1 3Δ state was studied, and the Fermi-contact interaction term for this state was determined to be ∼0.0111 cm−1.

Strain effects in GaN epilayers

A review is given about the influence of strain fields on the optical properties of GaN epilayers. We find the basic constant of the material: crystal field splitting, spin-orbit interaction parameter, deformation potentials. We discuss the evolution of the exciton binding energy with strain.

Spin-orbit interaction in a two-dimensional electron gas in a InAs/AlSb quantum well with gate-controlled electron density

We present experiments on the tuning of the spin-orbit interaction in a two-dimensional electron gas in an asymmetric InAs/AlSb quantum well using a gate. The observed dependence of the spin splitting energy on the electron density can be attributed solely to the change in the Fermi wave vector. The spin-orbit interaction parameter $(\ensuremath{\alpha}\ensuremath{\approx}0.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\mathrm{eV}\mathrm{}\mathrm{m})$ as such does not change significantly with electron density.

Gate Control of Spin-Orbit Interaction in an Inverted In0.53Ga0.47As/In0.52Al0.48As Heterostructure

We have confirmed that a spin-orbit interaction in an inverted I${\mathrm{n}}_{0.53}$G${\mathrm{a}}_{0.47}$As/I${\mathrm{n}}_{0.52}$A${\mathrm{l}}_{0.48}$As quantum well can be controlled by applying a gate voltage. This result shows that the spin-orbit interaction of a two-dimensional electron gas depends on the surface electric field. The dominant mechanism for the change in the spin-orbit interaction parameter can be attributed to the Rashba term. This inverted I${\mathrm{n}}_{0.53}$G${\mathrm{a}}_{0.47}$As/I${\mathrm{n}}_{0.52}$A${\mathrm{l}}_{0.48}$As heterostructure is one of the promising materials for the spin-polarized field effect transistor which is proposed by Datta and Das [Appl. Phys. Lett. 56, 665 (1990)].

Infrared diode laser spectroscopy of the ν1 fundamental and the ν1 + ν2 − ν2 sequence bands of the CCO radical

The infrared absorption spectrum of the CCO radical has been studied in an extension of the original observation of the CO stretching vibration by Yamada et al. [J. Chem. Phys. 84 (1985) 2573]. The CCO radical was generated using a flowing mixture of carbon suboxide and helium subjected to a hollow-cathode discharge. The spectral region between 1930–1990 cm −1 was probed using a tunable diode laser spectrometer. Transitions with N-values up to 40 were measured for the ν 1 fundamental and ν 1 + ν 2 − ν 2 sequence bands. Their analysis yielded band origins, rotational, centrifugal distortion, spin-spin interaction, and spin-orbit interaction parameters for the lower and upper vibrational states, and l-doubling parameters for the degenerate bending states ν 2 = 1 and ( ν 1 = 1, ν 2 = 1). In particular, the band origins for ν 1 and ν 1 + ν 2 − ν 2 were determined to be 1970.86332(41) cm −1 and 1960.13093(37) cm −1, respectively.

Investigation of the structure of the edge of the valence band of Cd1−x MnxS crystals on the basis of magnetooptical measurements

The results of magnetooptical studies are reported for Cd1−x MnxS crystals with concentrations of the magnetic component x 1=0.0056, and x 2=0.0013, x 1=0.0002 at T=2 K in a magnetic field H⩽3.5 T for H⊥c and H∥c, where c is the hexagonal axis of the crystal. The first reliable confirmation of spin splitting of the exciton reflection spectra of the B exciton transition is successfully obtained as a result of working in an H⊥c experimental geometry. The values of the crystal-field and spin-orbit interaction parameters Δ1, Δ2, Δ3 and the exchange constants J e and J h of Cd1−x MnxS crystals for achieving the best description of the experimental results in the mean exchange field approximation are found on the basis of the data obtained for H⊥c and for H∥c. An analysis shows that the main qualitative features of the observed reflection spectra for the entire series of investigated Cd1−x MnxS crystals can be described only if the condition (Δ1−Δ2)<0 is satisfied.

Electronic spectra of hexa aqua coordinated transition metal doped zinc struvite

Abstract Electronic spectra of nickel and cobalt doped ZnNH4PO4 .6H2O (Zinc struvite) crystals are recorded both at room and liquid nitrogen temperatures. In nickel doped host, bands are assigned to Ni(II) in octahedral symmetry whereas in cobalt doped host they are assigned to Co(II) in octahedral symmetry associated with spin orbit interaction. From the results and analysis, the following crystal field (Dq), interelectronic repulsion (B, C) and spin orbit interaction (ξ) parameters are evaluated. B = 930, Dq = 950 and C = 3550 cm−1 for Nickel ion and B = 870, Dq = 980 and C = 3830 cm−1, ξ = 500 cm−1 for cobalt ion.

Spin–Orbit Type Perturbations in theB(1)1Π State of ScCl: Characterization of the Interacting (1)3Σ+State

An extensive study of theB(1)1Π →X1Σ+system of45Sc35Cl and45Sc37Cl observed in high resolution spectra of the molecular thermal emission is presented. The rotational analysis reveals the presence of localized perturbations in almost all branches of bands withv′ ≤ 5, associated with hyperfine broadening of the perturbedQlines. These effects are interpreted as consequences of the avoided crossing betweenB(1)1Π(v) and (1)3Σ+(v+ 2) levels due to spin–orbit interaction. It appears possible to enter the interacting levels for both isotopomers in the same matrix representation, the energy term elements only involving equilibrium parameters of the states (isotopically scaled to45Sc35Cl). A semideperturbed model of the interacting states, taking account of the (v∼v+ 2) perturbations only, is first envisaged. The simultaneous fit of some 6600 line wavenumbers in 17 bands for45Sc35Cl and 7 bands for45Sc37Cl with a total standard deviation of 0.005 cm−1makes it possible to characterize the (1)3Σ+state and precisely describeB(1)1Π fromv= 0 tov= 5. Spin–orbit interaction parameters ξv,v+2are determined. A full deperturbation is then carried out using a model describing the levelsv= 0 tov= 7 of45Sc35Cl andv= 0 tov= 4 of45Sc37Cl for the two states, and taking account of all significant interactions. The following principal equilibrium molecular constants (in cm−1) are obtained: —for (1)3Σ+,[formula]The vibration-independent spin–orbit interaction parameter is directly determined, ξel= 53.02 cm−1.

Optical absorption spectra and laser analysis of Nd(III) in fluoroborate glasses

Absorption spectra of Nd 3+ ion in certain fluoroborate glasses have been studied and the spectroscopic parameters such as Racah ( E K ), spin-orbit ( ξ 4 f ) and configuration interaction (α) parameters have been calculated. From the intensity parameters ( Ω γ ) and from the squared reduced matrix elements (| U λ| 2 ), radiative transition probabilities ( A), branching ratios (β) and radiative life times ( τ R ) are calculated for the excited 4G 5 2 , 4G 7 2 , 4G 9 2 , 4F 5 2 , 4F 9 2 , 4F 3 2 and 2H 11 2 states of the Nd 3+ ion in fluoroborate glasses.

Effects of Strain Fields on Excitons and Phonons in Wurtzite GaN Epilayers

ABSTRACTThe electronic structure of a set of several tens of a few micrometer-thick GaN epilayers grown by MOVPE on (000l)-oriented sapphire is investigated by means of photoluminescence and reflectance spectroscopy. The strain-fields effects are quantitatively interpreted using a group theory analysis which predicts seven pertinent parameters: the crystal field splitting, two spin-orbit interaction parameters and four deformation potentials. From a theoretical point of view, we also examine the exciton problem. We establish the selection rules which control the strength of optical transitions for Г5 and Г1 excitons, and estimate the electron hole exchange interaction and the longitudinal transverse splitting of A, B, C excitons. Raman spectroscopy measurements are performed at various temperatures to observe the strain-induced shift of Raman frequencies. We determine four phonon deformation potentials in w-GaN.

Comparative analysis of free-ion energy levels of Er 3+ (4f 11) in various crystal hosts

The best energy level data available in the literature for the trivalent erbium-doped systems of about 30 crystal hosts are analysed in terms of a uniform model free-ion Hamiltonian H fi. H fi consists of 20 free-ion parameters which include the central field E avg, electrostatic repulsion F k ( k = 2, 4, 6), spin-orbit interaction parameter ξ, two-body configuration interaction parameters α, β and γ, three-body configuration interaction parameters T i ( i = 2, 3, 4, 6, 7, 8), spin—other-orbit interaction parameters M j ( j = 0, 2, 4) and electrostatically correlated spin-orbit interaction parameters P k ( k = 2, 4, 6). Our systematic theoretical analysis of crystal free-ion levels results in good correlation between calculated and observed energies. The reanalysis of some systems reported here yields improved fits of calculated to experimental energy levels compared with fits reported previously in the literature. The effects of the crystalline hosts on the empirical parameters are examined.

On the 3d Rydberg states of the NO molecule

We present a contribution to the study of the 3d Rydberg states of 14N16O based upon the analysis and treatment of infrared emission spectra of the H2Σ+, H′2Π → D2Σ+ (0-0) and (1-1) bands that we recorded at high resolution by Fourier transform spectroscopy. The 3d[σ(H2Σ+), π(H′2Π), δ(F2Δ)] complex representation is tested to determine the precision to which it is capable of reproducing the observed 3dσ, π and also the 3dδ term energy values (derived from the works of other authors). It appears that 3dσ, π terms, at least in the complex ν = 0, can be approximated to within experimental accuracy in a large range of J values (standard deviation of the residuals corresponding to some 165 levels, 0·005 cm-1). A similar precision is achieved for the 3dδ(ν = 0) terms when the F2Δ-B'2Δ interaction is taken into account. Deperturbed energies and rotational constants are obtained for the 3d(ν = 0 and 3d(ν = 1) states. Values of the spin-orbit and rotational interaction parameters within the 3d complexes ν = 0 and ...

The (5d10 + 5d96s) – 5d96p transitions in Tl IV, Pb V, and Bi VI

The spectra of thallium, lead, and bismuth were photographed in the region 600–2000 Å using sliding spark and triggered spark sources. The (5d10 + 5d96s)–5d96p transitions in Tl IV, Pb V, and Bi VI were investigated. Earlier level values were revised and new lines were classified. Hyperfine structure splittings were observed for many lines in Tl IV and Bi VI. Least squares fitted calculations were done for each spectra. The deviations between the calculated and observed level values showed that parametric descriptions using only the spin-orbit magnetic interaction parameter to describe magnetic effects is not sufficient in the 5d-shell spectra.

Spectroscopic investigations of the Pr(III) ion in certain ternary sulphate glasses

Ternary M-K-Zn (M ≡; Mg, Ca, Ba) sulphate glasses doped with 1 mol.% praseodymium sulphate were prepared by quenching. Absorption spectra were recorded for these glasses in the UV-visible and near-IR regions. The Racah, spin-orbit and configuration interaction parameters were evaluated by least-squares fit from the observed energies of the bands. Using Judd-Ofelt theory, theoretical intensity parameters, radiative lifetimes, branching ratios and absorption cross-sections were calculated for the excited 3P 1, 3P 0 and 1D 2 levels.

Zeeman splitting of double-donor spin-triplet levels in silicon.

Observation of the Zeeman effect has confirmed the identification of spin-triplet terms for double donors in silicon. The isotropic splitting of an absorption line at 2146.38 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in Si:${\mathrm{Se}}^{0}$, and of the corresponding line at 1218.37 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in Si:${\mathrm{Te}}^{0}$, into two \ensuremath{\sigma} components and one \ensuremath{\pi} component is consistent with their identification with the scrJ=1 spin-orbit level of the 1s(${A}_{1}$)1s(${T}_{2}$) configuration's $^{3}\mathrm{T}_{2}$ spin-triplet term. An experimental splitting factor ${g}_{\mathrm{scrJ}}$ of this line equal to 1.0 for both systems agrees with the theory of Land\'e g factors when the orbital g factor ${g}_{\mathrm{scrL}}$ equals zero as predicted by effective-mass theory. The spin-orbit interaction parameter determined from a nonlinear component in the Zeeman splitting predicts a ratio of singlet and triplet absorption strengths which agrees with the observed ratio to within a factor of 2 for Si:${\mathrm{Te}}^{0}$ but only to within a factor of 3 for Si:${\mathrm{Se}}^{0}$.

Optical studies of erbium(III) in certain sulphate glasses

Optical absorption spectra of erbium(III) ion in certain sulphate glasses have been studied for the first time in the UV-VIS and NIR regions. From the observed spectra, the spectroscopic parameters such as Racah ( E k ), spin-orbit ( ξ 4f ) and configuration interaction ( α ) parameters have been calculated by the method of least squares. The Judd-Ofelt intensity parameters ( Ω λ ) were determined from the observed oscillator strengths of the bands. Radiative transition probabilities ( A ), branching ratios ( β ), integrated cross sections ( Σ ) and radiative lifetimes ( τ ) are calculated for the excited fluorescent levels 4 I 13/2 , 4 I 11/2 , 4 I 9/2 , 4 F 9/2 , 4 S 3/2 , 4 F 7/2 , 4 F 7/2 , 4 F 5/2 , 2 H 9/2 and 4 G 11/2 of Er(III) in different sulphate glasses.