Analytical solutions of the microscopic two-band theory for the temperature dependence of the upper critical fields of pure MgB2 compared with experimental data

Abstract

Main theoretical results of the microscopic two-band theory for the temperature dependence of the upper critical fields H c2 (ab) and H c2 (c) in pure two-band systems like MgB 2 are presented. The analytical solutions for the upper critical fields near the superconducting transition temperature and near the zero temperature were transformed to be directly compared with experimental data. The experimental H c2 (ab) and H c2 (c) temperature dependences of textured MgB 2 films near the superconducting transition temperature were measured and compared with the respective theoretical formulas. The results of this theoretical approach were also compared with earlier published experimental data of other authors. The chosen method allows obtaining an accurate match between the theoretical expressions and experimental results.PACS: 74.20.-z Theories and models of superconducting state.

Two-gap s± -wave superconductivity at an oxide interface

“…in the OD regime is characteristic of multiband superconductors, as already discussed in other materials (e.g., MgB 2 [39] and Fe-based superconductors [40]) [41]. A similar behavior has sometimes been attributed to the presence of nodes in the superconducting gap, but this later possibility does not apply to LaAlO 3 /SrTiO 3 , for which superfluid stiffness measurements and tunneling spectroscopy show a nodeless gap structure [42][43][44].…”

Upper critical magnetic field in NbRe and NbReN micrometric strips

“…We find that while for NbRe the value of the critical field is purely orbital-limited, in the case of NbReN, the effect of the Pauli contribution plays a relevant role in the temperature dependence of H c2⟂ . We have not observed a positive curvature of H c2⟂ ( T ) near T c as it was in the case of two-band superconductivity [ 44 ] or proximity-coupled superconducting systems [ 45 – 46 ].…”