Investigation of carrier transport properties along the c-axis in K0.8Fe2Se2 superconducting crystals

Abstract

We have successfully prepared the iron-based superconductor K0.8Fe2Se2 crystals (Tc=27 K) and studied the carrier transport properties along the c-axis in detail. Samples are characterized by XRD, SEM and temperature-dependent resistivity. The result shows that there is “phase separation” in the samples. Based on the experimental results, the iron-based superconductor is not a simple two phases alternating along the c-axis, but the metal phases should have weak-link channels along the c-axis, forming a nearly 3D special net mode. Studies of the thermal conductivity and the complex impedance spectrum z(omega, T0) suggest that the superconducting crystals have a lot of grain boundaries along the c-axis direction, the bound polarization charges result in relative dielectric constant of about 106 in magnitude and negative phase characteristics in the vicinity of 10 MHz.

Electrochemical synthesis of alkali-intercalated iron selenide superconductors

“…For example, a series of superconductors A x (NH 3 ) y Fe 2 Se 2 (A = Li, Na, Ca, Sr, Ba, Yb, and Eu) have been successfully obtained by using liquid ammonia method, [1][2][3] which otherwise cannot be synthesized by the high-temperature route. [4][5][6][7][8][9][10][11][12] For Na x (NH 3 ) y Fe 2 Se 2 , enhanced superconducting transition temperature (T c ) of 46 K was observed. [1] The metal intercalation by other lowtemperature methods using pyridine, ethanediamine, and hexamethylenediamine as solvents was then demonstrated to be equivalently effective in inducing superconductivity with similar T c in Li x (C 5 H 5 N) y Fe 2−z Se 2 , [13] A x (C 2 H 8 N 2 ) y Fe 2−z Se 2 (A = Li, Na), [14,15] and Li x (C 6 H 16 N 2 ) y Fe 2−z Se 2 .…”