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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 (kappa_1 < 0.707) and type-2 (kappa_2 > 0.707) 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 gossamer-like vortex patterns that we have visualized in this type-1.5 superconductor using Bitter decoration and also reproduced in numerical simulations.
We demonstrate existence of non-pairwise interaction forces between vortices in multicomponent and layered superconducting systems. That is, in contrast to most common models, the interactions in a group of such vortices is not a universal superposit
We show that in multiband superconductors even small interband proximity effect can lead to a qualitative change in the interaction potential between superconducting vortices by producing long-range intervortex attraction. This type of vortex interac
In general a superconducting state breaks multiple symmetries and, therefore, is characterized by several different coherence lengths $xi_i$, $i=1,...,N$. Moreover in multiband material even superconducting states that break only a single symmetry ar
In the usual Ginzburg-Landau theory the critical value of the ratio of two fundamental length scales in the thery $kappa_c=1/sqrt{2}$ separates regimes of type-I and type-II superconductivity. The latter regime possess thermodynamically stable vortex
Usual superconductors are classified into two categories as follows: type-1 when the ratio of the magnetic field penetration length (lambda) to coherence length (xi) with Ginzburg-Landau parameter kappa=lambda/xi <1/sqrt{2} and type-2 when kappa >1/s