Vortex matter in lead nanowires

Stenuit, Geoffrey [UCL] Michotte, Sébastien [UCL] Govaerts, Jan [UCL] Piraux, Luc [UCL]

Theoretical and experimental magnetizations of lead nanowire arrays well below the superconducting transition temperature T-c are described. The magnetic response of the array was investigated with a SQUID magnetometer. Hysteretic behaviour and phase transitions have been observed in sweeping up and down the external magnetic field at different temperatures. The Meissner and Abrikosov states were also experimentally observed in this apparently type-I superconductor. This fact brings to the fore the non-trivial behaviour of the critical boundary K-c (= 1/root2 in bulk materials) between type-I and type-II phase transitions at mesoscopic scales. The time-independent Ginzburg-Landau equations particularized to cylindrically symmetric configurations enable one to explain and reproduce the experimental magnetization curves within 10% of error.