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 ξ 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 λ: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) andstates or between U (1) and U (1) × 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.

Fermi surface, possible unconventional fermions, and unusually robust resistive critical fields in the chiral-structured superconductor AuBe

“…Therefore, at low temperatures, AuBe seems to be a Type II superconductor with a Ginzburg-Landau parameter κ = λ/ξ, where λ is the London penetration depth and ξ is the coherence length, not much larger than 1/ √ 2, so that warming above 1.2 K leads to a transition to Type I behavior 45,50 . Similar behavior in disordered elemental superconductors was investigated thoroughly decades ago and was termed Type 1.5 or Type II/1 superconductivity 45,51,52 (κ ≈ 1/ √ 2), though it should be noted that the former term has more recently taken on a new meaning 53 . Recently, a similar suppression of the DPE in PdTe 2 with cooling below 1.5 K was attributed to screening via a superconducting surface layer 47 .…”

Melting of a two-dimensional monodisperse cluster crystal to a cluster liquid

“…Refs. [26][27][28][29]. For thin films an additional repulsive interaction arises due to magnetic stray fields that gives raise to vortex cluster crystals [13,23].…”

Multiply Quantized Vortices in Fermionic Superfluids: Angular Momentum, Unpaired Fermions, and Spectral Asymmetry

“…This can happen, for instance, in type-II mesoscopic superconductors, where MQVs have been predicted [15] and experimentally observed [16][17][18][19]. In addition, it has been argued that MQVs are expected to be energetically stable in multicomponent superconductors [20,21] and in chiral p-wave superconductors [22,23]. In fermionic SFs, a doubly quantized vortex was predicted [24] and observed in 3 He-A [25].…”