Acceptor excitation spectra in InSb

Optical excitation spectra of Zn, Cd and Ag acceptors in InSb have been measured. Excited state energies deduced from the spectra are in good agreement with effective mass theoretical predictions. Zeeman splitting of the spectra is consistent with the identification of the excitations, and strongly resembles the results obtained for acceptors in Ge.     

Thermo-emf of InSb in a transverse quantizing magnetic field

We have measured the thermo-emf of n-type indium antimonide in a transverse quantizing magnetic field. The results are explained using a theory that includes splitting of the Landau levels.Physics Institute of the Dagestanskii Center, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 26–29, March, 1993.     

High magnetic field helicon plasma discharge for plasma-wall interaction studies

正Dear Editors,Plasma-Wall Interactions(PWIs)are important for the development of magnetic confinement fusion devices such as International Thermonuclear Experimental Reactor(ITER),as they can release impurities into the plasma,erode the surfaces,or produce retention of fuel in the wall,among     

Light-response spectrum of a p-n junction of rediffused InSb in a magnetic field

The effect of a magnetic field (0–18 kG) on the spectral distribution of the photocurrent of p-n junctions obtained by the heat treatment of n-InSb in a vacuum is investigated. The reduced effective mass m^*/m₀=0.014 and the g-factor of the electrons (g=–50) are found from the spectral fluctuations of the photocurrent. A suggestion is advanced as to the exciton nature of the long-wavelength (LW) shift of the limit of the light response when the magnetic field is turned on. It has been established that the short-wavelength (SW) sensitivity is produced by photoelectrons of the p-layer and the sensitivity in the region of the LW limit is produced by photovacancies of the n-region.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 97–100, November, 1975.     

The magnetic field dependence of the PEM effect in melt-grown InSb thin layers

The room temperature dependence of the PEM effect on magnetic field has been measured in intrinsic, melt-regrown layers of InSb of thickness from 1 to 10 μm. When illuminated on the surface of higher recombination velocity (the back surface of the InSb layer) the samples showed an anomalous magnetic field dependence of the PEM effect. This was manifested in most of the samples as a sign reversal in the PEM voltage, from a negative voltage in weak magnetic fields to a positive voltage in strong fields. Since, theoretically, such a PEM voltage dependence might result from a strong dependence of the bipolar diffusion length L on the magnetic field H, several scattering mechanisms have been investigated to find the strongest dependence of L = L(H) in InSb layers. It has been found that the dependence L = L(H) could in no case be responsible for the experimental magnetic field dependence of the PEM effect. Good agreement between theory and experiment is reached if a magnetic field-dependent surface recombination velocity at the InSb-substrate interface is postulated. The shape of the dependence which gave the best fitting of theoretical to experimental results is given.     

The excitation spectrum of the one-dimensionalXY-model in a magnetic field

The exact excitation spectrum of theXY-model with a magnetic field inz-direction is considered in detail. If the exchange is exceeding the influence of the magnetic field, single fermion excitations are forbidden and at least two fermions have to be excited. The excitation spectrum is then continuous.     

ODD parity donor levels of germanium in a magnetic field

The lowest three odd parity states of Ge donors are calculated in the effective mass approximation as functions of magnetic field strength for fields in the (111) and (100) directions. This extends our earlier calculations of 1s and 2s-like Ge donor states. No simplifying assumptions are introduced —we attempt to take explicitly into account the lack of cylindrical symmetry of the effective mass Hamiltonian in our choice of trial functions. Our results appear to agree reasonably well with measured transition energies of Nisida and Horii.     

High magnetic field effects in some metallic magnetic materials

An account is given of the following magnetic properties in high magnetic fields: (1) Magnetic isotherms of pure nickel and Ni-Pd alloys near the Curie points; the exchange splitting energies deduced on this basis are discussed. (2) Metamagnetic transitions in internal fields for the rare earth-cobalt compounds R Co₂. (3) Metamagnetic transitions in external fields for Co(S, Se)₂ and ordered FePt₃.     

Mössbauer spectra of several magnetic sheet silicates in external magnetic field

Mössbauer spectra of nontronite, glauconite and montmorillonite recorded at temperatures down to 1.3 K and in applied fields of up to 4.5 T confirm that nontronite and glauconite are antiferromagnetic at 1.3 K. Glauconite becomes ferromagnetic in applied field. Fe^III ions in glauconite are deduced to be coupled ferromagnetically in the plane with alternate ferromagnetic planes coupled by a weak anti ferromagnetic interaction. Magnetic-hyperfine field distributions are computed for the magnetic spectra giving some indication of the relative disorder at particular iron sites.     

Correlation energy and excitation spectra of two-dimensional electron-hole systems in high magnetic fields

The correlation phenomena in two-dimensional semiconductors in high transverse magnetic fields are considered. A diagram expansion convergent at any temperatures T is obtained due to the special choice of an initial approximation. The expansion parameter appears equal to (E_o/T)exp(-E_o/2T) where E_o is the exciton binding energy. The expansion parameter of the usual Matsubara diagram technique would be proportional to 1/T, if the noninteracting electron-hole system were choosen as the initial approximation, due to the infinite degree of degeneracy of the ground state. The system proves equivalent to the slightly non-ideal exciton gas with the same long-wave properties as the two-dimensional Bose gas. The Hartree-Fock approximation is exact at T = 0, but there is no phase transition with a long-range order creation at T≠0 in contrast to the HFA results (although there remain some properties of the transition such as the maximum of specific heat etc.). The Berezinsky-Kosterlitz-Thouless transition is predicted in the system for very low temperatures. The diagram technique developed may be employed to treat the thermodynamics of other infinitely-fold degenerated systems.     

Exciton spectra of semiconductor superlattices in a parallel magnetic field

Low-temperature photoluminescence and photoluminescence excitation spectra of GaAs/AlGaAs semiconductor superlattices having different potential barrier widths (b=20, 30, 50, and 200 Å), i.e., degrees of tunnel coupling between quantum wells, are studied in magnetic fields up to 5 T oriented parallel and perpendicular to the layers of the structure. The changes in the qualitative character of the photoluminescence excitation spectra observed in a parallel magnetic field with increasing tunnel transparency of the barrier correspond to a transition from a quasi-two-dimensional to a quasi-three-dimensional electronic spectrum as a miniband develops in the superlattice. In the photoluminescence excitation spectra of the superlattice with b=50 Å, as the parallel magnetic field is increased, a new line appears in the violet wing of the spatially indirect exciton excitation line, which is absent in a perpendicular field. A similar line was also observed to arise in the photoluminescence spectra. It is shown that the indirect exciton luminescence line can be suppressed by both parallel and perpendicular magnetic fields.     

Collective rearrangement of spin excitation spectrum of antiferromagnet with magnetic impurities in external magnetic field

Antiferromagnetic resonance (AFMR) in Co_1?cMn_cF₂ (c ～ 10^-4) in the external magnetic field is investigated. It was established that coherent and incoherent rearrangements (CR and ICR) of spectrum in the region of AFMR and impurity lines crossing are possible in the same sample depending on field orientation. Topology of the phase diagram of spin excitation (SE) spectrum in variables c-H is obtained.     

Parametric excitation of a magnetic nanocontact by a microwave field

We demonstrate that magnetic oscillations of a current-biased magnetic nanocontact can be parametrically excited by a microwave field applied at twice the resonant frequency of the oscillation. The threshold microwave amplitude for the onset of the oscillation decreases with increasing bias current, and vanishes at the transition to the auto-oscillation regime. Theoretical analysis shows that measurements of parametric excitation provide quantitative information about the relaxation rate, the spin transfer efficiency, and the nonlinearity of the nanomagnetic system.     

Magneto-reflectance spectra of anisotropic CdS by magnetic field modulation

Reflectance spectra of CdS in high magnetic fields perpendicular to the C-axis are reported. A modulation technique has been used with an external modulating magnetic field to detect the signal derivative. The forbidden n = 1 excitons Γ₆(A-edge) and Γ₂(B-edge) have been observed. Transitions between Landau levels with ΔN ≠ 0 have been identified.     

High magnetic field researches in Tohoku University

Using hybrid magnets for fields up to 31 T, superconducting magnets up to 20 T and cryogen-free magnets up to 15 T, characterization of superconductors, materials synthesis and condensed matter physics are being done in the High Field Laboratory for Superconducting Materials. We have developed thin strong superconducting wire, which enable us to construct compact magnet, cryogen-free magnet and cryogen-free hybrid magnet for the first time. We have found that polymer materials, high T_c superconductors and protein single crystals synthesized in high magnetic fields show different characters from those synthesized in normal condition. Magnetic levitation is performed to make a microgravity condition for materials processing similar to the space.     

Anomalous spin excitation spectrum of the Heisenberg model in a magnetic field

Making the assumption that high-energy fermions exist in the two dimensional spin- 1/2 Heisenberg antiferromagnet, we present predictions based on the pi-flux ansatz for the dynamic structure factor when the antiferromagnet is subject to a uniform magnetic field. The main result is the presence of gapped excitations in a momentum region near (pi,pi) with energy lower than that at (pi,pi). This is qualitatively different from spin-wave theory predictions and may be tested by experiments or by quantum Monte Carlo.     

强磁场中Rydberg NO分子的回归谱研究

利用分子的闭合轨道理论和多通道量子亏损理论,考虑核的转动影响,计算了Rydberg NO分子在外磁场中的回归谱.研究表明,复杂谱的结构可以用包含分子实散射的闭合轨道理论来解释,不管是同一通道内的弹性散射还是不同通道间的非弹性散射都起着非常重要的作用,尤其是较大标度作用量下,散射作用远大于基本轨道和重复轨道的贡献,很大程度上影响着体系的动力学性质。     

InSb纳米晶体的生长和吸收光谱的研究

采用在惰性气体中蒸发的方法获得了沉积在ZnS基片上的InSb纳米晶体,其平均尺寸随惰性气体的压强增加而增大.从实验测量的室温吸收谱上看到,当纳米晶体的平均直径从27.9 nm减小到24.2nm再到21.4 nm时,其吸收边分别向高能方向移动了0.0151 eV和0.0145 eV.用有效质量近似模型计算了半导体纳米晶体的吸收边相对其体材料的移动,将理论计算与实验结果进行了比较.