Vortex pinning in two-gap superconductors

We discuss vortices and their pinning in two-gap superconductors, in which two superconducting gaps are opened around two different Fermi surfaces. We found that there are two kinds of vortices with continuously valuable fractions of the unit flux quanta hc/2e. These two kinds of vortices are tightly bound and cannot be separated in the ground state, but can be when deconfinement occurs by the finite temperature effect as is pointed out (See, Jun Goryo, Shingo Soma, and Hiroshi Matsukawa, Europhys. Lett. 80 (2007) 17002). In this paper, we show that two kinds of vortices can be split by the pinning effect.