Apokamps produced by repetitive discharges in air

New experimental and computational data on apokamps produced by repetitive discharges in air, including a detailed description of the research techniques used, are presented. It has been shown that plasma bullets–streamers in apokamps at low frequencies could start not only from the bright offshoot but also directly from the discharge channel. The experimental and computational data demonstrate that the visual color of apokamp changes from blue to red as the intensity ratio of the second to the first positive nitrogen system decreases with the decreasing pressure

Ginzburg-Landau Analysis for the Antiferromagnetic Order in the Fulde-Ferrell-Larkin-Ovchinnikov Superconductor

Incommensurate antiferromangetic (AFM) order in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductor is investigated on the basis of the Ginzburg-Landau theory. We formulate the two component Ginzburg-Landau model to discuss two degenerate incommensurate AFM states in the tetragonal crystal structure. Owing to the broken translation symmetry in the FFLO state, a multiple phase diagram of single-q phase and double-q phase is obtained under the magnetic field along [100] or [010] direction. Magnetic properties in each phase are investigated and compared with the neutron scattering and NMR measurements for a heavy fermion superconductor CeCoIn_5. An ultrasonic measurement is proposed for a future experimental study to identify the AFM-FFLO state. The field orientation dependence of the AFM order in CeCoIn_5 is discussed.Comment: 8 page

Locally Non-centrosymmetric Superconductivity in Multilayer Systems

Although multilayer systems possess global inversion symmetry, some of the layers lack local inversion symmetry because no global inversion centers are present on such layers. Such locally non-centrosymmetric systems exhibit spatially modulated Rashba spin-orbit coupling. In this study, the superconductivity in multilayer models exhibiting inhomogeneous Rashba spin-orbit coupling is investigated. We study the electronic structure, superconducting gap, and spin susceptibility in the superconducting state with mixed parity order parameters. We show the enhancement of the spin susceptibility by Rashba spin-orbit coupling and interpret it on the basis of the crossover from a centrosymmetric superconductor to a non-centrosymmetric superconductor. It is also shown that the spin susceptibility is determined by the phase difference of the order parameter between layers and is nearly independent of the parity mixing of order parameters. An intuitive understanding is given on the basis of the analytic expression of superconducting order parameters in the band basis. The results indicate that not only a broken global inversion symmetry but also a broken local inversion symmetry leads to unique properties of superconductivity. We discuss the superconductivity in artificial superlattices involving CeCoIn5 and multilayer high-Tc cuprates.Comment: 11 pages, 13 figures, final version for publication in J. Phys. Soc. Jp