Anisotropic field dependence of the electronic transport in superconducting FeSe thin films

Abstract

Electronic transport measurements were carried out on c-axis oriented epitaxial FeSe thin films in static magnetic fields up to 14 T parallel to the crystallographic c-axis and parallel to the ab-plane. The temperature dependence of the upper critical fields B c c2 and B ab c2 was determined from the field dependence of the resistivity. While B c c2 was orbitally limited, the larger B ab c2 was paramagnetically limited. The anisotropy γ B was decreasing with decreasing temperature and revealed a pseudoisotropic behaviour towards zero temperature. This temperature dependence is indicative of the multiband character of FeSe. From measurements of the temperature-and field-dependent critical current densities the effective depinning or irreversibility field B * c2 was obtained, and its angular dependence yielded the effective mass anisotropy γ m . The temperature dependence of γ m , which was different from that of γ B , can be considered as another signature of multiband FeSe.

Multi-band analysis on physical properties of superconducting FeSe films

“…[30] Moreover, the anisotropy of the upper critical fields decreases with the decreasing temperature and reveals a pseudoisotropic behavior in this process, which is also indicative of the multi-band character for this material. [31] The strong temperature dependence of Hall sensitivity for the FeSe film shows the similar effect. [32] Thus, there is still no general consensus on the form of superconducting order parameter in the FeSe film to date, and further explorations to elucidate this issue are necessary.…”

Boundary Effect and Critical Temperature of Two-Band Superconducting FeSe Films

“…At around 100 K, FeSe shows a structural phase transition from tetragonal to orthorhombic without an accompanying magnetic phase transition and becomes superconducting below 8 K [2,[5][6][7]. The picture of two-gap superconductivity has been clearly confirmed by the scanning tunneling microscopy measurements, multiple Andreev reflection spectroscopy, specific heat measurements and other experiments [8][9][10][11][12].…”