Type-1.5 superconductor
Type-1.5 superconductors are multicomponent superconductors characterized by two or more coherence lengths, at least one of which is shorter than the magnetic field penetration length λ {\displaystyle \lambda } , and at least one of which is longer. This is in contrast to single-component superconductors, where there is only one coherence length ξ {\displaystyle \xi } and the superconductor is necessarily either type 1 ( ξ > λ {\displaystyle \xi >\lambda } ) or type 2 ( ξ < λ {\displaystyle \xi <\lambda } ) (often a coherence length is defined with extra 2 1 / 2 {\displaystyle 2^{1/2}} factor, with such a definition the corresponding inequalities are ξ > 2 λ {\displaystyle \xi >{\sqrt {2}}\lambda } and ξ < 2 λ {\displaystyle \xi <{\sqrt {2}}\lambda } ).