Robust superconductivity and transport properties in (Li1-x Fe x )OHFeSe single crystals

Abstract

The recently discovered (Li1−xFex)OHFeSe superconductor with Tc about 40K provides a good platform for investigating the magnetization and electrical transport properties of FeSe-based superconductors. By using a hydrothermal ion-exchange method, we have successfully grown crystals of (Li1−xFex)OHFeSe. X-ray diffraction on the sample shows the single crystalline PbO-type structure with the c-axis preferential orientation. Magnetic susceptibility and resistive measurements show an onset superconducting transition at around Tc=38.3K. Using the magnetization hysteresis loops and Bean critical state model, a large critical current Js is observed in low temperature region. The critical current density is suppressed exponentially with increasing magnetic field. Temperature dependencies of resistivity under various currents and fields are measured, revealing a robust superconducting current density and bulk superconductivity.

Long-range magnetic order in hydroxide-layer-doped (Li1−x−yFexMnyOD)FeSe

“…This phenomena was observed in previous works as well and can be at- tributed to the vortex dynamics in the system 8,59,60,63 . The residual resistivity ratio ρ(300K)/ρ(T c ) for the sample presented is ∼ 25 which is higher than in previous reports 8,[60][61][62] . The observed normal state behavior is non-linear which has been demonstrated in previous works 8, [60][61][62] and has been attributed to over-doping in the sulfide analogue 64 .…”

“…Specifically where this behavior has been justified by strong vortex flow as well as a wide temperature range for vortex liquid behavior due to anisotropy and two-dimensionality. 8,39,58,[60][61][62][63] The superconducting onset temperature measured by resistivity is much higher than in the same crystal measured in magnetic susceptibility. This phenomena was observed in previous works as well and can be at- tributed to the vortex dynamics in the system 8,59,60,63 .…”

Protonation induced high- T c phases in iron-based superconductors evidenced by NMR and magnetization measurements

“…Protonation in FeS leads to a high superfluid density, similar to that of FeSe 0.93 S 0.07 . The FeSe-based compounds has caused a lot of research interests lately because of their highly tunable T c [35][36][37][38]. As discussed earlier, the Hebel-Slichter coherence peak is absent in the 1/T 1 at T c1 and at T c2 .…”

Band structure reconstruction across nematic order in high quality FeSe single crystal as revealed by optical spectroscopy study

“…The PbO-type FeSe has the simplest structure in iron-based superconductors with a stack of edge-sharing FeSe 4 -tetrahedra layer by layer. The undoped FeSe exhibits superconducting transition at T c ∼9 K, but it can easily reach 37 K upon applying hydrostatic pressure 1 and over 40 K by intercalating space layers 2,3 . The T c of the single layer FeSe film grown on SrTiO 3 (STO) has been reported to be ∼60−70 K in angle-resolved photoemission spectroscopy (ARPES) experiments [4][5][6][7] and Meissner effect measurements 8,9 .…”