Anomalous magnetic field reversal in laser-plasma interactions

Two-dimensional numerical results are presented for laser produced carbon plasmas evolving through the formation of the critical surface. These results show a novel reversal of the spontaneously generated magnetic field.     

Electromagnetic wave interactions in a strong permanent magnetic field

The interaction of electromagnetic waves in a strong permanent magnetic field is considered in the frame of the parameterized nonlinear electrodynamics of a vacuum. The dispersion relations for normal modes are derived. As well, the effect of nonlinear corrections on ring-laser generation frequencies is calculated. Original Russian Text ? V.A. Sokolov, 2009, published in Vestnik Moskovskogo Universiteta. Fizika, 2009, No. 3, pp. 108–110.     

Spin-lattice relaxation in solid 3He in weak magnetic fields

Spin-lattice relaxation times T ₁ were measured for solid ³He at temperatures of 0.22 to 0.73 K in a 44-Oe magnetic field. An increase in T ₁ at temperatures higher than approximately 0.4 K was related to switching on the vacancy mechanism of atomic mobility in the crystal. At a melting curve minimum, in the region of predominance of exchange motions of atoms in the crystal, measurements of T ₁ were performed in magnetic fields of 2 to 71 Oe. The data obtained in fields higher than 5 Oe were in agreement with the Cowan-Fardis theory.     

Coherent atom interactions mediated by dark-state polaritons

We suggest a technique to induce effective, controllable interactions between atoms that is based on Raman scattering into an optical mode propagating with a slow group velocity. The resulting excitation corresponds to the creation of spin-flipped atomic pairs in a way that is analogous to correlated photon emission in optical parametric amplification. The technique can be used for fast generation of entangled atomic ensembles, spin squeezing, and applications in quantum information processing.     

Self-consistent method for interactions mediated by fields

A self-consistent procedure for treating a system of Fermions interacting via the exchange of virtual mesons is described.     

Spontaneously self-organized structures by magnetic interactions

For heavy-fermion superconductivity a new alternate mechanism of magnetic origin and of antiferromagnetic nature has been found. By using nonperturbative methods it is explicitly shown that a system of itinerant electrons interacting through Heisenberg's exchange interaction can undergo a phase transition from the paramagnetic state either to superconducting or to magnetically ordered state depending on whether the coupling constant is negative or positive.Dedicated to Academician Vladimír Hajko on the occasion of his 65th birthday.     

Reversible electron-induced cis-trans isomerization mediated by intermolecular interactions

Reversible isomerization processes are rarely found when organic molecular switches are adsorbed on metal surfaces. One obstacle is the large energy difference of the isomeric forms, since usually the most planar conformer has the largest adsorption energy. In the example of an imine derivative, we show a strategy for also stabilizing the non-planar isomer by intermolecular bonding to its neighbors. Tunneling electrons from the tip of a scanning tunneling microscope can then be used to induce reversible switching between the trans?and cis-like state. Supported by model force-field calculations, we illustrate that the most probable cause of the enhanced stability of the three-dimensional cis?state at specific adsorption sites is the electrostatic interaction with N sites of the neighboring molecule.     

Planar spin chain with competing interactions in an external magnetic field

The 1D classical planar model with nearest neighbor (NN) and next nearest neighbor (NNN) competing interactions is studied at finite temperature in presence of an external magnetic field by the transfer matrix method. In particular we are interested into helix configurations supported by an exchange competition strong enough. The short range order (SRO) is strictly related to the zero temperature long range order (LRO). Our exact calculation makes possible the comparison with the current expectation that a discontinuous helix-fan transition occurs before the continuous fan-collinear transition takes place. This feeling is based on the extrapolation of low field-high field zero temperature expansions. We find strong evidence that this expectation is fulfilled when the turn angle of the helix is lesser than /2, whereas for turn angles greater than /2 the discontinuous transition does not take place and the helix changes continuously to a collinear configuration as the magnetic field is increased. Our conclusion is based on the analysis of the SRO at finite temperature exactly calculated by the transfer matrix method and on the zero temperature exact calculation of the minimum energy of commensurate configurations.     

Quantum mechanics in theK-field formalism: Account of interactions with magnetic field

Using the K-field formalism, quantum equations are derived for a particle in a random stationary electromagnetic field. It is shown that this field can enter the K-field expression only via the |v(xⁱ)|² functions (the squared classical velocity of the K-particle). Tomsk Polytechnical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 55–57, October, 1999.     

One-spin quantum logic gates from exchange interactions and a global magnetic field

It has been widely assumed that one-qubit gates in spin-based quantum computers suffer from severe technical difficulties. We show that one-qubit gates can, in fact, be generated using only modest and presently feasible technological requirements. Our solution uses only global magnetic fields and controllable Heisenberg exchange interactions, thus circumventing the need for single-spin addressing.     

Fictitious magnetic resonance by quasielectrostatic field

We propose a new kind of spin manipulation method using a fictitious magnetic field generated by a quasielectrostatic field. The method can be applicable to every atom with electron spins and has distinct advantages of small photon scattering rate and local addressability. By using a CO₂ laser as a quasielectrostatic field, we have experimentally demonstrated the proposed method by observing the Rabi oscillation of the ground state hyperfine spin F=1 of the cold ⁸⁷Rb atoms and the Bose–Einstein condensate.