A structurally-controllable spin filter in a δ-doped magnetically modulated semiconductor nanostructure with zero average magnetic field

We report on a theoretical investigation of spin-polarized transport in a δ-doped magnetically modulated semiconductor nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe on the top of a semiconductor heterostructure and by using the atomic layer doping technique such as molecular beam epitaxy (MBE). It is shown that although such a nanostructure has a zero average magnetic filed, a sizable spin polarization exists due to the Zeeman splitting mechanism. It is also shown that the degree of spin polarization varies sensitively with the weight and/or position of the δ-doping. Therefore, one can conveniently tailor the behaviour of the spin-polarized electron by tuning the δ -doping, and such a device can be employed as a controllable spin filter for spintronics.     

Can η mesons have a magnetic moment?

The response of pseudoscalar and vector mesons to strong magnetic fields is studied within a simple constituent quark model using analogy with bound states of Positronium. Magnetic moments of charged vector mesons K*, D*, B* are predicted and it is found that η mesons have magnetic polarizability. In extremely strong magnetic fields, behaviour of J/Ψ mesons is discussed. We speculate on the existence of an induced magnetic moment of η meson.     

Geometric phase of spin-1 in a rotating magnetic field

The quantum phase and the related fields have attracted considerable attention. The geometric phase of spin-1/2 particle in the magnetic field has been discussed comprehensively, but few of spin-1. In this paper, the exact solution of spin-1 was obtained by using rotational frame method. The problems of the Rabi oscillation, dynamical phase, and geometric phase were solved.     

The ising model in a magnetic field of ½iπ

The result of Lee and Yang for the free energy of a square two-dimensional Ising model in a magnetic field of ½iπ is shown to be correct only if the thermodynamic limit is approached through even numbers of lattice sites. Derivations of this result are given by the algebraic (Onsager-Kaufman) method and the fermion operator (Hurst) method.     

Spectrum of Schrödinger field in a noncommutative magnetic monopole

The energy spectrum of a nonrelativistic particle on a noncommutative sphere in the presence of a magnetic monopole field is calculated. The system is treated in the field theory language, in which the one-particle sector of a charged Schrödinger field coupled to a noncommutative U(1) gauge field is identified. It is shown that the Hamiltonian is essentially the angular momentum squared of the particle, but with a nontrivial scaling factor appearing, in agreement with the first-quantized canonical treatment of the problem. Monopole quantization is recovered and identified as the quantization of a commutative Seiberg–Witten mapped monopole field.     

Cauchy magnetic field component and magnitude distribution studied by the zero‐field muon spin relaxation technique

Zero‐field muon spin relaxation (ZF‐μSR) data for dilute spin magnetic systems have been widely interpreted with what is called a Kubo–Toyabe form based on a Lorentzian distribution of local field components. We derive here the proper magnetic field magnitude distribution using independent and uncorrelated component distributions. Our result is then compared to the previously accepted formula for ZF‐μSR. We discuss the origins of the magnetic field component and magnitude distributions. Further, we found that after rescaling the magnetic field, the differences that are amenable to experimental examination are quite small, although the interpretations behind them are quite different. This revised version was published online in August 2006 with corrections to the Cover Date.     

Do neutrinos have mass?

Limits on neutrino masses are discussed, both from kinematical considerations (3-body weak decays, etc.) and from dynamical neutrino mass effects (oscillations). The Dirac versus Majorana question is addressed as well and typical limits from neutrinoless double-beta decay are presented.     

Do semiclassical zero temperature black holes exist?

The semiclassical Einstein equations are solved to first order in epsilon = Planck's over 2pi/M2 for the case of a Reissner-Nordstr?m black hole perturbed by the vacuum stress energy of quantized free fields. Massless and massive fields of spin 0, 1/2, and 1 are considered. We show that in all physically realistic cases, macroscopic zero temperature black hole solutions do not exist. Any static zero temperature semiclassical black hole solutions must then be microscopic and isolated in the space of solutions; they do not join smoothly onto the classical extreme Reissner-Nordstr?m solution as epsilon-->0.     

Radiation from relativistic electrons during entry into a magnetic field andβ decay in the field

This paper considers the radiation emitted when a nucleus experiences decay in a magnetic field, producing relativistic electrons. The spectral-angular distribution of the radiation from relativistic electrons in a sharply delineated magnetic field was also found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 92–95, March, 1976.In conclusion, the authors express their gratitude to Prof. A. A. Sokolov for the stimulating interest he took in the paper and extend their thanks to V. Ch. Zhukovskii for his helpful discussion of the results obtained.     

Does there arise a significant enhancement of the dynamical quark mass in external magnetic field?

Recently, it was found in QED that the generation of a dynamical electron mass in a strong magnetic field is significantly enhanced by the perturbative electron mass. In the present Letter, the related question of a possible enhancement of the dynamical quark mass in an external magnetic field and with a bare mass term is investigated in the Nambu–Jona-Lasinio model.     

Bloch electrons in a magnetic field: why does chaos send electrons the hard Way?

We find that a 2D periodic potential, with different modulation amplitudes in the x and y directions, and a perpendicular magnetic field may lead to a transition to electron transport along the direction of stronger modulation and to localization in the direction of weaker modulation. In the experimentally accessible regime we relate this new quantum transport phenomenon to avoided band crossings due to classical chaos.     

Vibrational transition spectra of H2＋ in a strong magnetic field

Vibrational transition spectra of H2+ in an ultra-strong magnetic field are determined. The validity of Born-Oppenheimer approximation is analyzed based on one-center method and B-spline basis sets. It is shown that Born-Oppenheimer approximation is reliable for the investigation on the ground state and low excited states of H2+ subjected to the strong magnetic field. Furthermore, it is found that the vibrational transition spectra from 1σ g , 1π u , and 1δ g states lie in infrared, visible, and ultraviolet ranges with increasing magnetic field strength.     

A disordered two-dimensional system in a magnetic field: Borel-Padé analysis

We report on a calculation of the density of states and the diffusion constant for the lowest Landau level for an electron moving in two dimensions in a random potential, and under a strong magnetic field. The calculation is based on renormalized perturbation expansion carried out to very high orders, which is summed using the method of Borel-Padé analysis. The results are obtained from an extensive series analysis involving 45 terms in the white noise case and 36 terms in the case of a spatially correlated random potential.     

Superconductivity in SnO: a nonmagnetic analog to Fe-based superconductors?

We discovered that under pressure SnO with α-PbO structure, the same structure as in many Fe-based superconductors, e.g., β-FeSe, undergoes a transition to a superconducting state for p?6 GPa with a maximum Tc of 1.4 K at p=9.3 GPa. The pressure dependence of Tc reveals a domelike shape and superconductivity disappears for p?16 GPa. It is further shown from band structure calculations that SnO under pressure exhibits a Fermi surface topology similar to that reported for some Fe-based superconductors and that the nesting between the hole and electron pockets correlates with the change of Tc as a function of pressure.     

Fluorescence spectra of uranium induced by a linearly polarized laser light in a magnetic field

In this paper we reported the fluorescence spectra of U~(238) induced by a linearly polarized laser field in a magnetic field and offered a theoretical analysis. The consistence between the theoretical prediction and experimental results was satisfactory.     

Magnetotransport study of in situ magnetic field textured Dy1Ba2Cu3O7−δ superconductors

The electrical resistivity, thermoelectric power and the Nernst effect have been studied as a function of temperature and magnetic field for a typical superconductor DyBa₂Cu₃O_7– magnetically textured in situ at 1035°C. The three transport coefficients show hybrid microscopic features. In particular, we show the anisotropy with respect to the field direction (H//a,H//c) in all transport coefficients. We verify that Tinkham's law is obeyed for the broadening of the resistive transition in a magnetic field. Similarly we obtainanisotropic broadening exponents for each integrated excess property. From Arrhenius plots we obtain orders of magnitude for the activation energies characterizing each property. They are markedly different from each other.