DC C-axis Electrical Resistivity of FeSe Superconductor

Superconductivity in iron pnictides is an area of interest for the condensed-matter community. The relatively high critical temperature ($T_{C})$ of 26 K first observed in 2008 in one of these materials offered new opportunities for research. Iron (II) selenide (FeSe), which has the simplest crystal structure among the iron-based superconductors (FeSC) has a $T_{C}$ of about 8 K. FeSe, because of its simple crystal structure, is a material at the center of understanding the superconducting mechanism in FeSCs. Understanding the electrodynamics of FeSe is one such focus. Previously, no known measurements have been made of the DC c-axis electrical resistivity although the resistivity in the ab-plane of FeSe is well-documented. This study is aimed at measuring this quantity using standard experimental procedures which include a four-wire measurement and the modified Corbino method for electrical contacts. This study found that the magnitude of the resistivity in the c-axis direction is much greater than in the ab-plane as expected. Further, the resistivity as a function of temperature illustrates values of $T_{C}$ and the structural transition temperature, $T_{S}$, that agrees with values observed with ab-plane measurements.