AC susceptibility study of superconducting aluminium-doped silicon carbide

In 2007, type-I superconductivity in heavily boron-doped silicon carbide was discovered. The question arose, if it is possible to achieve a superconducting phase by introducing dopants different from boron. Recently, aluminum-doped silicon carbide was successfully found to superconduct by means of resistivity and DC magnetization measurements. In contrast to boron-doped silicon carbide, the aluminum doped system is treated as a type-II superconductor because of the absence of an hysteresis in data measured upon decreasing and increasing temperature in finite magnetic fields. In this paper, results of a recent AC susceptibility study on aluminum-doped silicon carbide are presented. In higher applied DC magnetic fields and at low temperatures, a weak indication of supercooling with a width of a few mK is found. This supports the conclusion that aluminum-doped silicon carbide is located near to the border between type-I and type-II superconductivity, as pointed out in a recent theoretical work, too.