Evolution of the Pauli spin-paramagnetic effect on the upper critical fields of single-crystallineKxFe2−ySe2−zSz

Abstract

We have studied the temperature dependence of the upper critical fields, µ0Hc2, of KxFe2−ySe2−zSz single crystals up to 60 T. The µ0Hc2 for H ab and H c decrease with increasing sulfur content. The detailed analysis using Werthamer-Helfand-Hohenberg (WHH) theory including the Pauli spin-paramagnetic effect shows that µ0Hc2 for H ab is dominated by the spinparamagnetic effect, which diminishes with higher S content, whereas µ0Hc2 for H c shows a linear temperature dependence with an upturn at high fields. The latter observation can be ascribed to multiband effects that become weaker for higher S content. This results in an enhanced anisotropy of µ0Hc2 for high S content due to the different trends of the spin-paramagnetic and multiband effect for H ab and H c, respectively.

Superconducting monolayer deposited on substrate: Effects of the spin-orbit coupling induced by proximity effects

“…In the WHH theory T c is found as a function of a parameter describing the system [85], e.g., it can be the SO coupling. Similarly as the findings of the present work, the WHH theory predicts that an increase of the spin-orbit coupling can lead to an increase of T c [86]. Moreover, similar behavior of T c can be observed in systems with non-trivial p-wave pairing [87].…”

Tuning orbital-selective correlations in superconductingRb0.75Fe1.6Se2−zSz

“…The isoelectronic substitution of selenium with sulfur leads to the reduction of the superconducting transition temperature and the upper critical fields in K 1−x Fe 2−y Se 2−z S z . 14,15 With respect to the observed hierarchy of temperatures T met = 90 K, T gap = 61 K and T c = 32 K, the evolution of these temperature scales with varying sulfur content will provide important information on how orbital-selective correlation effects influence the onset of superconductivity.…”