Fluctuations in two-band superconductors in a strong magnetic field

Abstract

We consider the behaviour of the fluctuating specific heat and conductivity in the vicinity of the upper critical field line for a two-band superconductor. Multiple-band effects are pronounced when the bands have very different coherence lengths. The transition to superconductive state is mainly determined by the properties of the rigid condensate of the "strong" band, while the "weak" band with a large coherence length of the Cooper pairs causes the nonlocality in fluctuation behaviour and break down of the simple Ginzburg-Landau picture. As expected, the multiple-band electronic structure does not change the functional forms of dominating divergencies of the fluctuating corrections when the magnetic field approaches the upper critical field. The temperature dependence of the coefficients, however, is modified. The large in-plane coherence length sets the field scale at which the upper critical field has upward curvature. The amplitude of fluctuations and fluctuation width enhances at this field scale due to reduction of the effective z-axis coherence length. We also observe that the apparent transport transition displaces to lower temperatures with respect to the thermodynamic transition. Even though this effect exists already in a single-band case at sufficiently high fields, it may be strongly enhanced in multiband materials.

15 pages, 1 figure, submitted to the Superconductor Science and Technology, special issue on Multicomponent Superconductivity

References in corpus (13)

• High-temperature superconductivity in iron-based materials
• Upper critical fields and thermally-activated transport of Nd(O_0.7F_0.3)FeAs single crystal
• Superfluid density and specific heat within self-consistent scheme for two-band superconductor
• Psuedo-isotropic upper critical field in cobalt-doped SrFe2As2 epitaxial films
• Decrease of upper critical field with underdoping in cuprate superconductors
• Giant Nernst Effect due to Fluctuating Cooper Pairs in Superconductors
• Multiband effects on beta-FeSe single crystals
• Phase textures induced by dc current pairbreaking in multilayer structures and two-gap superconductors
• Multiorbital effects on the transport and the superconducting fluctuations in LiFeAs
• Microscopic analysis of the superconducting quantum critical point: Finite temperature crossovers in transport near a pair-breaking quantum phase transition
• Fluctuation conductivity of thin films and nanowires near a parallel-field-tuned superconducting quantum phase transition
• Anisotropic fluctuations and quasiparticle excitations in FeSe_0.5Te_0.5
• Fluctuation conductivity in disordered superconducting films

Cited by in corpus (6)

• Emergent phenomena in multicomponent superconductivity: an introduction to the focus issue
• Ground state, collective mode, phase soliton and vortex in multiband superconductors
• Vortex-lattice melting and paramagnetic depairing in the nematic superconductor FeSe
• Quasi-2D behavior of 112-type iron-based superconductors
• Enhanced superconducting-fluctuation effects on thermodynamic properties in BCS-BEC-crossover regime
• Large increase of the anisotropy factor in the overdoped region of Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$ as probed by fluctuation spectroscopy