title: Type-1.5 superconductivity.
abstract: We demonstrate the existence of a novel superconducting state in high quality two-component MgB2 single crystalline superconductors where a unique combination of both type-1 (lambda{1}/xi{1}<1/sqrt[2]) and type-2 (lambda{2}/xi{2}>1/sqrt[2]) superconductor conditions is realized for the two components of the order parameter. This condition leads to a vortex-vortex interaction attractive at long distances and repulsive at short distances, which stabilizes unconventional stripe- and gossamerlike vortex patterns that we have visualized in this type-1.5 superconductor using Bitter decoration and also reproduced in numerical simulations.
authors.affiliation: INPAC-Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium. victor.moshchalkov@fys.kuleuven.be
authors.forename: Victor
authors.initials: V
authors.lastname: Moshchalkov
authors.forename: Mariela
authors.initials: M
authors.lastname: Menghini
authors.forename: T
authors.initials: T
authors.lastname: Nishio
authors.forename: Q H
authors.initials: QH
authors.lastname: Chen
authors.forename: A V
authors.initials: AV
authors.lastname: Silhanek
authors.forename: V H
authors.initials: VH
authors.lastname: Dao
authors.forename: L F
authors.initials: LF
authors.lastname: Chibotaru
authors.forename: N D
authors.initials: ND
authors.lastname: Zhigadlo
authors.forename: J
authors.initials: J
authors.lastname: Karpinski