Abstract
All superconductors in a magnetic field are characterized by three critical magnetic fields: lower critical Hc1, upper critical Hc2 and thermodynamic critical field Hc. Only two sets of inequalities Hc2 > Hc > Hc1 or Hc1 > Hc > Hc2 are possible in a single-component superconductor. Here, we report our study of the critical fields in multicomponent superconductors with two superconducting components in the framework of the Ginzburg-Landau functional. We derive the relationship between the phases of the components of the superconducting complex order parameter from the charge conservation law in explicit form and insert it into the Ginzburg-Landau functional. Using the modified Ginzburg-Landau equation, we acquire the single vortex state including the analytical expression for asymptotics. Also, we obtain the analytical form for the state in the upper critical field. We find that in some cases an unusual sequence of critical fields Hc1, Hc2 > Hc can be realized in multicomponent superconductors.