title: Oscillatory behavior of vortex-lattice melting transition line in mesoscopic Bi_{2}Sr_{2}CaCu_{2}O_{8+y} superconductors.
abstract: The vortex-lattice melting transition of a limited number of vortices confined in mesoscopic square superconductors was studied by c-axis resistance measurements using stacks of intrinsic Josephson junctions in Bi_{2}Sr_{2}CaCu_{2}O_{8+y}. In contrast to the melting transition in bulk crystals, we have first found a clear oscillatory behavior in the field dependence of the melting temperature in small samples of 5-10  μm square. The periods of the oscillations roughly obey the regularity of the matching conditions of square vortex lattices surrounded by a square boundary and the melting temperatures are enhanced around the vortex number of i^{2} (where i is an integer). The results suggest that a confinement effect by the square boundary stabilizes square lattice structures which are realized around i^{2} vortex number even in competition with the favorable Abrikosov triangular lattice in the bulk.
authors.affiliation: National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ooi
authors.affiliation: National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Mochiku
authors.affiliation: National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tachiki
authors.affiliation: National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hirata