Yuzephovich O. Vortex lattice commensurability effects in superconducting layered systems

Object - artificial superconducting superlattices (SL) Mo/Si, limited thickness SL V/Si, thin V films. Goal -clarification of structural features of vortex lattices (VL) and revealing the structural phase transitions in mixed state in layered superconductors and thin films. Method -Measurements of resistive transitions and critical currents. -Results, novelty - The resistive method is proposed as a tool for the VL structure study in layered superconductors. It is applicable to all layered superconductors and can be used in strong magnetic fields. -Novel phenomenon of zero resistance reentrance from resistive state is discovered on Mo/Si SL. This is explained in terms of the intrinsic pinning and VL commensurability with SL period. -The effect of commensurability between VL parameter and film thickness is observed in homogeneous films. -Two different commensurability effects between both the VL parameter and the SL period and sample thickness are observed simultaneously in limited thickness V/Si SL. -The lock-in transition is observed on SL and thin V films. The temperature dependence of the critical angle for lock-in state is determined firstly. -The avalanche-type jumps of the resistivity have been observed at first time on the Mo/Si SL with thick Si layers. The model is proposed which explains the jump patterns as the manifestation of the phase transitions between various commensurate states of the VL. employment - fundamental science, novel materials.