Quasi-Two-Dimensional Nature of High-T _c Superconductivity in Iron-Based (Li,Fe)OHFeSe

Abstract

The intercalated iron selenide (Li,Fe)OHFeSe has a strongly layered structure analogous to the quasi two-dimensional (2D) bismuth cuprate superconductors, and exhibits both high-temperature (T c) and topological superconductivity. However, the issue of its superconductivity dimensionality has not yet been fully investigated so far. Here we report that the quasi-2D superconductivity features, including the high anisotropy γ = 151 and the associated quasi-2D vortices, are also revealed for (Li,Fe)OHFeSe, based on systematic experiments of the electrical transport and magnetization and model fittings. Thus, we establish a new vortex phase diagram for (Li,Fe)OHFeSe, which delineates an emergent quasi-2D vortex-liquid state, and a subsequent vortex-solid dimensional crossover from a pancake-like to a three-dimensional state with decreasing temperature and magnetic field. Furthermore, we find that all the quasi-2D characteristics revealed here for the high-T c iron selenide superconductor are very similar to those reported for the high-T c bismuth cuprate superconductors.

Recent progress on epitaxial growth of Fe-based superconducting thin films

“…The relationship to vortex phases in more 2D cuprates, such as BSCCO, is focus of recent investigations regarding transport anisotropy. Indeed, in a recent publication [51], Li et al showed that (Li,Fe)OHFeSe is equally anisotropic as BSCCO with H c2 anisotropies around 150 close to T c with 2D-like angular dependence of H c2 , which allowed completing and explaining the vortex phase diagram within the vortex glass region. With the help of relaxation measurements and J c maxima (determined via magnetization), the transition between a 3D vortex solid and quasi-2D pancake vortices was determined.…”