Type-1.5 superconductivity in multicomponent systems

Abstract

In general a superconducting state breaks multiple symmetries and, therefore, is characterized by several different coherence lengths ${\xi }_i$, $i=1,...,N$. Moreover in multiband material even superconducting states that break only a single symmetry are nonetheless described, under certain conditions by multi-component theories with multiple coherence lengths. As a result of that there can appear a state where some coherence lengths are larger and some are smaller than the magnetic field penetration length $\lambda$: ${\xi }_1\le {\xi }_2...<\sqrt{2}\lambda <{\xi }_M\le ...{\xi }_N$. That state was recently termed "type-1.5" superconductivity. This breakdown of type-1/type-2 dichotomy is rather generic near a phase transition between superconducting states with different symmetries. The examples include the transitions between $U(1)$ and $U(1)\times U(1)$ states or between $U(1)$ and $U(1)\times Z_2$ states. The later example is realized in systems that feature transition between s-wave and $s+is$ states. The extra fundamental length scales have many physical consequences. In particular in these regimes vortices can attract one another at long range but repel at shorter ranges. Such a system can form vortex clusters in low magnetic fields. The vortex clustering in the type-1.5 regime gives rise to many physical effects, ranging from macroscopic phase separation in domains of different broken symmetries, to unusual transport properties.

v2: Missing value for a coupling constant for Fig 2(d) added. Prepared for the proceedings of Vortex IX conference, Rhodes 12-17 September 2015. Updates and supersedes the Vortex VII proceedings contribution arXiv:1110.2744

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Cited by in corpus (1)

• Locking of length scales in two-band superconductors