Vortex molecule, fractional flux quanta, and interband phase difference soliton in multi-band superconductivity and multi-component superconductivity

Abstract

Variety of a vortex and lattice of vortex in two-component superconductivity are addressed. The balance between an energy gain of the magnetic energy forming the "sub-unit flux quantum" and cost for inter-component Josephson interaction deforms an axisymmetric vortex into a non-axisymmetric one, which is a so-called vortex molecule. To deal with this situation, a crude formalism is introduced, in which London equation for magnetic field and a sine-Gordon equation for the inter-component Josephson interaction are separated. Giving an attention to the Josephson interaction, we introduce a "quantum-phase domain".