International Journal of Modern Physics B

In the present interdisciplinary review, we focus on the applications of the symmetry principles to quantum and statistical physics in connection with some other branches of science. The profound and innovative idea of quasiaverages formulated by N. N. Bogoliubov, gives the so-called macro-objectivation of the degeneracy in the domain of quantum statistical mechanics, quantum field theory and quantum physics in general. We discuss the complementary unifying ideas of modern physics, namely: spontaneous symmetry breaking, quantum protectorate and emergence. The interrelation of the concepts of symmetry breaking, quasiaverages and quantum protectorate was analyzed in the context of quantum theory and statistical physics. The chief purposes of this paper were to demonstrate the connection and interrelation of these conceptual advances of the many-body physics and to try to show explicitly that those concepts, though different in details, have certain common features. Several problems in the field of statistical physics of complex materials and systems (e.g., the chirality of molecules) and the foundations of the microscopic theory of magnetism and superconductivity were discussed in relation to these ideas.

In the present paper, we study the influence of simultaneous polarized optical treatment (10 ns Nd: YAG lasers with wavelengths 1064 nm and 532 nm with power density 0.6 GW/cm²) together with electrostatic dc electric field (up to 8 kV/cm) on self-assembled multi-layer film samples. The second-order optical susceptibility (SOS) achieves the maximal values after one minute simultaneous dc electrical-optical treatment. Further treatment will not enhance the values and even leads to the decrease of SOS. The independent measurement of the local temperature shows that local heating does not exceed 10.1 K.

In the present paper, an influence of the anisotropic antisymmetric exchange interaction, the Dzialoshinskii–Moriya (DM) interaction, on entanglement of two qubits in various magnetic spin models, including the pure DM model and the most general XYZ model, are studied. We find that the time evolution generated by DM interaction can implement the SWAP gate and discuss realistic quasi-one-dimensional magnets where it can be realized. It is shown that inclusion of the DM interaction to any Heisenberg model creates, when it does not exist, or strengthens, when it exists, the entanglement. We give physical explanation of these results by studying the ground state of the systems at T = 0. Nonanalytic dependence of the concurrence on the DM interaction and its relation with quantum phase transition is indicated. Our results show that spin models with the DM coupling have some potential applications in quantum computations and the DM interaction could be an efficient control parameter of entanglement.

We present a comprehensive investigation of the equilibrium structural, electronic and magnetic properties of Co₂MnSi and Co₂FeSi by density-functional theory (DFT) within the generalized gradient approximation (GGA) using the projected augmented wave (PAW) method. The on-site Coulomb interaction has also taken into account (GGA+U) approach to unravel the correlation effects on the electronic structure. The change of the energy gap, "spin gap", Fermi energy level and magnetic moments with the lattice parameters is investigated. We found that the on-site correlation interaction in Co₂FeSi is stronger than in Co₂MnSi. So on-site electronic correlation is necessary for Co₂FeSi and the magnetic moments reproduce experimental results well by GGA+U. Further we also found that a moderate change of the lattice parameters does not change the half-metallic ferromagnet (HMF) behavior for both materials. Appearance of half-metallicity is consistent with the integral magnetic moments, which also agrees with the experiment measurements.

A heterostructure of a semi-infinite metal and a Mott insulator is considered. It is supposed that both materials have an identical lattice spacing and hopping integrals and differ in the Hubbard repulsion, which is negligible in the metal and exceeds the critical value for the Mott transition in the insulator. At half-filling and for low temperatures, the insulator has the long-range antiferromagnetic order. Its low-lying elementary excitations are standing spin waves and a spin-wave mode which is localized near the interface and has a two-dimensional dispersion. This mode ejects bulk modes from the boundary region. The antiferromagnetic ordering of the insulator induces an antiferromagnetic order in the metal where the magnetization decays exponentially with distance from the interface. This decay is characterized by the correlation length equal to 5–6 lattice spacings.

Various metal film systems, deposited on liquid (silicone oil) substrates by thermal evaporating and DC-magnetron sputtering methods, have been successfully fabricated and the stress relief mechanisms are systematically studied by analyzing the characteristic surface morphologies. The experiment shows that the evaporating metal films can move on silicone oil surfaces freely due to the nearly zero adhesion of solid–liquid interface, which results in spontaneous formation of ordered surface patterns with a characteristic sandwiched structure driven by the internal stress. For the sputtering metal film system, however, the top surface of silicone oil can be modified to form an elastomeric polymer layer on the liquid substrate during deposition. Subsequent cooling of the system creates a higher compressive stress in the film, which is relieved by buckling of the film to form periodic wavy structures because the adhesion of solid–elastomer interface is quite strong.

Divergence exponents of the first-order quantum correction of a two-dimensional hard-sphere Bose atoms are obtained by an effective field theory method. The first-order correction to the ground-state energy density with respect to the zeroth-order is given by , where D is the spatial dimension, and γ is the gas parameter (γ = na^D). As D →2, α = α′ = 1. We show that the first-order quantum correction of the energy density is not perturbative in low dimensions of D < 2.2 regardless of any gas parameter which is much less than unity.

A Liouville integrable multi-component integrable system is obtained by the vector loop algebra. Then, the integrable couplings of the above system are presented by using the expanding vector loop algebra of the . Finally, the bi-Hamiltonian structure of the obtained system is given, respectively, by the variational identity.