Upper critical magnetic field of KxFe2−ySe2and Eu

Abstract

The H -T phase diagrams of single crystalline electron-doped K 0.83 Fe 1.83 Se 2 (KFS1), K 0.8 Fe 2 Se 2 (KFS2) and hole-doped Eu 0.5 K 0.5 Fe 2 As 2 (EKFA) have been deduced from tunnel diode oscillator-based contactless measurements in pulsed magnetic fields up to 57 T for the interplane (H c) and in-plane (H ab) directions. The temperature dependence of the upper critical magnetic field H c2 (T ) relevant to EFKA is accounted for by Pauli model including an anisotropic Pauli paramagnetic contribution (μ B H p = 114 T for H ab and 86 T for H c). This is also the case of KFS1 and KFS2 for H ab whereas a significant upward curvature, accounted for by a two-gap model, is observed for H c. Despite the presence of antiferromagnetic lattice order within the superconducting state of the studied compounds, no influence of magnetic ordering on the temperature dependence of H c2 (T ) is observed.

(Li1−xFex)OHFeSe Superconductors: Crystal Growth, Structure, and Electromagnetic Properties

“…Iron-based superconductors (FeSCs) have attracted much attention because of their diverse structures, complex phases, and unconventional superconductivity [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. FeSCs have the highest superconducting (SC) transition temperatures (T c ) after cuprate SCs, above the generally accepted McMillan limit of 39 K predicted by Bardeen-Cooper-Schrieffer (BCS) theory, opening up new opportunities for exploring novel high-T c SCs [17].…”

Upper critical field with magnetic and non-magnetic scattering*

“…A feature of these curves worth noting is the nearly linear temperature dependence over a broad temperature range. This feature occurs in many iron-based materials (Ni et al, 2008;Gasparov et al, 2013). Our work therefore suggests that the near-linear behavior of H c2 ðTÞ might be related to pair breaking.…”

“…The reduced field h(t) for the pair-breaking scattering parameter ρ m0 5 1, the parameter a 5 0.1 and the transport scattering ρ 5 0, 2, and 5. Note the extended nearlinear domains of h(t) and the upturn at low temperatures, the features seen in a number of Fe-based materials (Ni et al, 2008;Gasparov et al, 2013).…”

Magnetic field dependence of high-Tcinterface superconductivity inLa1.55Sr0.45Gasparov1, Drigo2, Audouard3 et al. 2016Phys. Rev. BSelf Cite3000View full textAdd to dashboardCite

“…After signal amplification, mixing with a reference signal and demodulation, the resulting oscillator frequency, which can be approximated by f = 1/(2π√LC), lies in the MHz range. As the magnetic field increases, the tunnel-diode oscillator tracks the shift in the resonant frequency that increases upon entering the normal state, giving a clear indication of the superconducting-to-resistive state transition 26,27 .…”