Type-1.5 Superconductor - Type-1.5 Superconductivity in Multiband Systems

Type-1.5 Superconductivity in Multiband Systems

In a two-band superconductor the electrons in different bands do not independently conserved thus the definition of two superconducting components is different. A two-band superconductor is described by the following Ginzburg-Landau model

F=\sum_{i,j=1,2}\frac{1}{2m} |(\nabla - ie A) \psi_i|^2 + \alpha_i |\psi_i|^2 + \beta_i|\psi_i|^4 - \eta( \psi_1\psi_2^* + \psi_1^*\psi_2) + \gamma + \nu |\psi_1|^2|\psi_2|^2 +\frac{1}{2}(\nabla \times A)^2

where again are two superconducting condensates. In multiband superconductors quite generically . When three length scales of the problem are again the London penetration length and two coherence lengths. However in this case the coherence lengths are associated with "mixed" combinations of density fields.

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