I. D. Vagner

Recent trends in theory of physical phenomena in high magnetic fields

Preface. I: Superconductors, organics and normal metals. The interlayer magnetoresistance in quasi-2D layered organic metals P.D. Grigoriev, M.V. Kartsovnik, W. Biberacher, N.D. Kushch, P. Wyder. The interplay of superconductivity and nuclear magnetism T. Herrmannsdorfer, F. Pobell. Magnetic domains with non-spin origin: Condon domains in berylium and silver J. Hinderer, A.G.M. Jansen. MgB2: superconductivity and pressure effects V.A. Ivanov, J.J. Betouras, F.M. Peeters. Pairing transition in a normal Fermi system with attractive interactions M. Keller, W. Metzner, U. Schollwock. The vortex liquid state in a 2D superconductor at high magnetic fields T. Maniv, V. Zhuravlev. II: Quantum Hall and nano systems. 20 years since the discovery of the fractional quantum Hall effect M.I. Dyakonov. Dimensional crossover in 2D crossbars K. Kikoin, I. Kuzmenko, S. Gredeskul, Y. Avishai. Quantum effects in the conductivity of a quasi 2D electron gas M. Levanda, V. Fleurov. Excitons in single and vertically coupled type II quantum dots in high magnetic fields F.M. Peeters, K.L. Janssens, B. Partoens. Size dependent properties of nanoscale particles (silica) I. Schweigert, M.J. Carrier, M.R. Zachariah. Contact phenomena in 2D electron systems in the quantum Hall effect regime V.B. Shikin. III: Spintronics and hyperfine interaction. III.1. Electron spins. Spin transport in diluted magnetic semiconductors superlattices M. Bejar, D. Sanchez, G. Platero, A.H. MacDonald. Magnetic impurities in a strong magnetic field P.D. Dahan, V. Fleurov, K. Kikoin, I.D. Vagner. Hall effect and magnetoresistance in p-type ferromagnetic semiconductors T. Dietl, F.Matsakura, H. Ohno, J. Cibert, D. Ferrand. Spin effects in quantum Hall droplets P. Hawrylak. III.2. Nuclear spins. On deriving relaxation equations for nuclear spins W. Appel, Yu.A. Bychkov. NMR revisited P. Averbuch. Electron spectrum in nuclear spin polarization induced periodic structures B. Lembrikov, P. Malits, M. Haridim, A. Kaplunovsky, I.D. Vagner. Nuclear-spin-polarization-induced low-dimensional electron structures Yu.V. Pershin. Isotopically engineered Si as a promising material for spintronics and semiconductor-based nuclear spin quantum computers I. Shlimak, I.D. Vagner. Nuclear spintronics I.D. Vagner. IV: Wave propagation and magneto-active media. Dimensional crossover and dissipation of helicon waves and QHE electrodynamics E. Potemska, O. Timofeevskaia, I.D. Vagner, P. Wyder. Recent trends in the theory of magneto-scattering of light B.A. van Tiggelen, G.L.J.A. Rikken, F.A. Pinheiro, D. Lacoste. List of Contributors. Author Index. Subject Index.

Magnetooscillations in a superconductor

Abstract We consider the possibility of observing quantum oscillatory phenomena in a type II superconductor, i.e., at fields B ≤ H c 2 , the upper critical field. We find that standard magnetooscillation probes will remain effective. The presence of Landau levels should, however, alter the nature of the states which are paired. In turn, the superconductivity can modify the oscillations, by contributing additional frequencies.

Condon domains as sine-Gordon solitons

Magnetic domains and the de Haas-van Alphen effect are considered on the basis of the sine-Gordon equation being of Lagrange-Euler form for magnetic induction. The kink (soliton) solution obtained describes the domain walls of Condon domains. Calculations of the domain wall width and energy are carried out.

Magneto-oscillations in YBa2Cu3O7-δ in high magnetic fields

Abstract Magneto-oscillatory signals have been observed in the magnetization of samples of oriented YBa 2 Cu 3 O 7− δ powders. The experiments have been performed in pulsed magnetic fields up to 52 T. The Fourier transform of these signals analyzed as a function of 1/ B is dominated by two peaks at frequencies very close to the dHvA frequencies reported by Fowler et al. (Phys. Rev. Lett. 58 , 534 (1992)). The field dependence of the amplitude of the oscillations is in qualitative agreement with that predicted by a recent theory of Maniv et al .

Magnetooscillations in quasi-two-dimensional extreme type II superconductors

Abstract We present a generalization of Gorkovs derivation of the Ginsburg-Landau equation for a quasi 2D superconductor which includes the effect of a strong quantizing magnetic field. We find that quantum oscillations should persist in the superconducting state, and hence that dHvA oscillations should be observable at sufficiently low temperature.

Fast incomplete decoherence of nuclear spins in a quantum Hall ferromagnet

A scenario of quantum computing process based on the manipulation of a large number of nuclear spins in Quantum Hall (QH) ferromagnet is presented. It is found that vacuum quantum fluctuations in the QH ferromagnetic ground state at filling factor � = 1 , associated with the virtual excitations of spin waves, lead to fast incomplete decoherence of the nuclear spins. A fundamental upper bound on the length of the computer memory is set by this fluctuation effect. PACS numbers: A growing number of models for quantum information processing (or Quantum Computing-QC) has been recently proposed 1 , some of which were successfully tested experimentally in devices consisting of a few qbits.The scaling up of these toy devices to the desired large number of quantum gates seems at present a formidable challenge. Of special interest are the models based on the manipulation of nuclear spins in semiconducting

Thermo- and magnetic-field-induced dynamics of ferroelectric interphase boundaries

Abstract Thermo- and magnetic-field-induced dynamics of first-order ferroelectric and antiferroelectric phase transitions are considered, taking into account the inertia effect. The width and velocity of interphase boundaries are calculated as functions of temperature and magnetic field strength. The results obtained here are essentially different from those of the Ginzburg-Landau theory and of the case of the small kinetic energy term, and they may also be used for the description of the kinetics of ferroelectric phase transitions in high-temperature superconductive perovskites.

Nuclear spin-lattice relaxation in quasi 2D-systems: The role of impurity scattering

Abstract Our theory of the nuclear spin-relaxation in a quasi-two-dimensional electron gas under the quantum Hall effect conditions (see: I.D. Vagner and T. Maniv, Phys. Rev. Lett 61 (1988) 1400) is generalized to take into account explicitly the impurity scattering within framework of the finite temperature diagram technique. For sufficiently sharp Landau levels and low temperatures we recover the simple Lorentzian smearing of the energy conservation condition in the flip-flop process assumed previously.

Spatial spin distribution of a skyrmion in a two-dimensional electron gas at a small g-factor

The effect of a weak Zeeman spin splitting on the spatial distribution and the energy of an isolated skyrmion in a 2D electron gas under a strong magnetic field at filling factor is studied within the framework of the Hartree-Fock approximation. Finite Zeeman splitting introduces two different characteristic lengths into the problem, corresponding to the tail and the core of the spin distribution. The non-linear differential equation for the macroscopic spin density associated with the skyrmion is solved in the limit of very small g-factor, for which the tail of the skyrmion is much longer than its core radius. In this limit the Coulomb repulsion energy of the skyrmion, which determines the core radius, does not affect the shape of the spin distribution.

Order parameter induced phase shift in the dHvA oscillations in type-II superconductors

Abstract In a pure type-II superconductor under a strong magnetic field every Landau level around the Fermi energy, which is significantly broadened by the pair potential at low temperatures, splits into two major magnetic subbands. Such a splitting reflects the fact that the magnetic flux threading a unit cell in the Abrikosov lattice is one half electronic flux quantum. This effect is predicted to be observed as a rapid 180° phase shift in the de Haas-van Alphen(dHvA) oscillations just below H c 2 , and is expected to be sensitive to disorder and vortex lines motion.