Investigation of level crossing in the tetragonal paramagnet YbPO4 in ultrahigh magnetic fields up to 400 T

The crossing of the energy levels of Yb³⁺ ions in paramagnetic YbPO₄ in ultrahigh magnetic fields of up to 400 T, produced by an explosive method, is investigated experimentally and theoretically. A wide maximum is found in the differential susceptibility dM/dH in a field H _c ≈280 T. This maximum is due to the crossing of the energy levels of the magnetic ions in the field. The magnetocalorimetric effect is calculated under the assumption that the magnetization process in the pulsed fields is adiabatic. The effect is nonmonotonic as a function of the field and is accompanied by a substantial cooling of the crystal near H _c . Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 691–694 (10 May 1997)     

Grantmakher-Kaner effect in strong magnetic fields

Gantmakher-Kaner (GK) effect in a compensated metal is studied theoretically. The dependence of the amplitude of GK oscillations from the polarization of exciting radio-frequency field is found. Effect results from the excitation of doppleron in the plate. In polarization, in which the doppleron exists, the part of skin-layer field energy, contained in harmonics with the length close to cyclotron displacement of resonant carriers, is carried into the slab by doppleron. This results in decreasing of GK oscillations in this polarization in comparison with an opposite one.     

Exciton condensation in strong magnetic fields

The density correction to the chemical potential of excitons in a strong magnetic field was calculated. The possibilities of Bose-Einstein condensation of excitons and their condensation into electron-hole liquid (EHL) were studied. Magnetic field ranges in which these processes can be observed were determined.     

Coulomb collisions in strong magnetic fields

Summary Scattering cross-sections, reflection and transmission coefficients are derived for charged-particle potential scattering in the presence of a quantizing constant magnetic field within the Green's function approach. The optical theorem and the limit of the cross-section for vanishing values of the magnetic field have also been obtained. A numerical analysis of the total cross-section for different magnetic-field intensities and values of the screening constant has been performed. The total cross-sections are found to differ significantly from the field-free ones only for magnetic-field intensities and incident particle energies such that only few Landau channels are open. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Radiative process in strong magnetic fields

Abstract

The behavior of electromagnetic processes in strong magnetic fields is currently of great interest in high-energy astrophysics. Observations of neutron stars indicate that magnetic fields larger than 10¹² Gauss exist in nature. In fields this strong, where electrons behave much as if they were in bound atomic states, familiar processes undergo profound changes and exotic processes become important. Strong magnetic fields affect the physics in several fundamental ways: energies prependicular to the field are quantized, transverse momentum is not conserved and electron/positron spin is important. The relaxation of transverse mometum conservation allows first order processes and their inverses: one-photon pair production and annihilation, synchrotron/cyclotron radiation and absorption, which are kinematically forbidden under field-free conditions. The first two are essentially quantum-mechanical and hence significant only in fields whose strength approaches the critical field, B _cr = 4.414 × 10¹³ Gauss. One-photon pair production is likely to be the dominant source of e ⁺ -e ^? pairs in fields exceeding 10¹² Gauss. While synchrotron radiation and absorption are observable as classical electromagnetic processes in weak fields, they are considerably different in high fields, where the classical synchrotron radiation formulae can violate conservation of energy, and predict too large an emissivity and electron energy loss rate. The second-order processes: two-photon pair production and annihilation and Compton Scattering, are also modified in strong fields. The discreteness of e ⁺ - e^? pair states causes resonant behavior in the cross sections and decreases the second-order rates from their free-space values. These processes play an important role in modelling high energy emission from pulsars and gamma-ray bursts.     

Andreev reflection in strong magnetic fields

We have studied the interplay of Andreev reflection and cyclotron motion of quasiparticles at a superconductor-normal-metal interface with a strong magnetic field applied parallel to the interface. Bound states are formed due to the confinement introduced by both the external magnetic field and the superconducting gap. These bound states are a coherent superposition of electron and hole edge excitations similar to those realized in finite quantum-Hall samples. We find the energy spectrum for these Andreev edge states and calculate transport properties.     

Magnetoresistance and Hall effect of the magnetic semiconductor HgCr2Se4 in strong magnetic fields

The giant decrease of the electrical resistance of HgCr₂Se₄ (more than by a factor of 200) caused by magnetic field-induced changes in the carrier mobility and concentration, the quadratic dependences of magnetoresistance and normal Hall constant on magnetic induction in the paramagnetic region, as well as the deviations from these dependences observed to occur as one approaches the Curie temperature, are discussed within a model involving carriers of several types (holes in the valence band, electrons localized at ferron-type impurity centers, and electrons hybridized in the impurity and conduction bands). Fiz. Tverd. Tela (St. Petersburg) 39, 848–852 (May 1997)     

Screening of impurities in strong magnetic fields

Charged impurities inserted in an electron gas in strong magnetic fields and at low temperatures are considered. Using the random phase and the generalized Born approximations, a self-consistent calculation of the screening of the impurities and the broadening of the electronic energy levels due to the scattering by these impurities is presented. Concrete results obtained in numerical form show that for typical semiconductors the anisotropy of te screening induced by the magnetic field is strongly reduced by collisional damping. The screening length, however, depends rather strongly on the field.On leave of absence from the Department of Physics, University of Tokyo, Tokyo, Japan.     

Anisotropy of atoms in strong magnetic fields

The anisotropy of the atomic electronic density caused by strong magnetic fields is discussed here in the context of the statistical theory. In the framework of the current-density functional theory, a derivation is given of the gradient terms, necessary for anisotropy, based on the polarizability of free electrons in a magnetic field. Numerical results for the electronic density show a strong elongation of the electronic density along the field direction. In very high magnetic fields the electronic density is localized in thin columns along the field.     

Two-dimensional excitonic phase in strong magnetic fields

The excitonic phase of the coupled electron-hole system which consists of p- and n-channel inversion layers separated by a thin insulating layer and subjected to a strong magnetic field, is investigated in the mean field approximation. The spectrum of the symmetry-restoring collective excitation mode is shown to be consistent with the possible superfluidity of excitons.     

Martensitic phase transitions in strong magnetic fields

The model of linear chains is used to study the lattice softening of A 15-compounds in strong magnetic fields. It is shown that a strong field stabilizes the cubic phase due to the Zeeman energy of the conduction electrons. Experiments are suggested to test our theoretical findings.     

Cold and ultracold Rydberg atoms in strong magnetic fields

Cold Rydberg atoms exposed to strong magnetic fields possess unique properties which open the pathway for an intriguing many-body dynamics taking place in Rydberg gases, consisting of either matter or anti-matter systems. We review both the foundations and recent developments of the field in the cold and ultracold regime where trapping and cooling of Rydberg atoms have become possible. Exotic states of moving Rydberg atoms, such as giant dipole states, are discussed in detail, including their formation mechanisms in a strongly magnetized cold plasma. Inhomogeneous field configurations influence the electronic structure of Rydberg atoms, and we describe the utility of corresponding effects for achieving tightly trapped ultracold Rydberg atoms. We review recent work on large, extended cold Rydberg gases in magnetic fields and their formation in strongly magnetized ultracold plasmas through collisional recombination. Implications of these results for current antihydrogen production experiments are pointed out, and techniques for the trapping and cooling of such atoms are investigated.     

Dielectric response and kohn effect in strong magnetic fields

The dielectric polarization of an electron gas in strong magnetic field is calculated in the random phase approximation for finite temperatures and finite impurity concentrations. For parameter values typical for semiconductors a remarkable enhancement of the dielectric response at critical wave lengths and, consequently, of the Kohn anomaly has been found.