Thermal Fluctuations of Order Parameters in Two-Gap Superconductors

Multicomponent superconductivity based on multiband superconductors

“…The very weak interband interaction (on the order of a few percent of the maximum strength of the intraband interaction) can reproduce the second broad peak in the heat capacity, but the moderately weak interband interaction (on the order of ten percent of the maximum strength of intraband interaction) does not reproduce it. These anomalous thermodynamic properties and gap evolutions were revisited theoretically by Vargunin, T Örd, and K Rägo in 2011 [85] and 2013 [86]. The abnormal gap evolution in a two-component superconductivity based on multiband superconductors was experimentally reported as an abnormal temperature dependence of the superfluid density estimated by the penetration depth using the muon-spin rotation (μSR) technique for FeSe 1−x [87].…”

Two-gap superconductivity: interband interaction in the role of an external field

“…An effect of interband pairing is most intriguing in the situation when the joint superconducting state is close to splitting into two independent condensates. In this case the memory of intrinsic criticality of the weaker band becomes very pronounced and visible in the temperature scale as an additional maximum or a kink in the heat capacity curve [20][21][22][23][24][25], coherence lengths [26][27][28], relaxation times [29], conductivity [30] and superfluid density data [31,32]. An inflection point appears in the temperature behaviour of the weaker-band gap which was observed in a number of two-gap materials [5,[33][34][35][36][37][38][39].…”

Shrinking of the fluctuation region in a two-band superconductor

“…Note also that restricting ourselves to considering uniform spatial mode only (i.e. homogeneous system), thermal fluctuations in a finite-size two-band superconductor reveal already the memory of the former autonomous phase transition in the band with weaker superconductivity [47].…”