Superconductivity in the K-Mo-O system*

The rutile-type structure belongs to space group P4$_{2}$\textit{/mnm}. Some transition metals form dioxides with variants rutile structure are known as pseudorutiles. These dioxides have interesting physical properties but they are still poorly understood. MoO$_{2}$ is one of them. Polycrystalline samples of MoO$_{2}$ can be easily prepared using stoichiometric amounts of Mo and MoO$_{3}$ through solid state reaction at temperatures near 700\r{ }C. This material is a highly conductive oxide and exhibits Mo-Mo metallic bounds along $c$-axis. On the other hand, previous results show that the physical properties of the MoO$_{2}$ are substantially changed with potassium doping [1]. This work unambiguously demonstrates that the K$_{x}$MoO$_{2}$ system exhibits superconductivity. Electrical resistivity and magnetization measurements were carried out from 2 to 300 K. The electrical and magnetic measurements show that the superconducting critical temperature ranges from 3 to 10 K. The phase composition responsible for the superconductivity is still under investigation. \\[4pt] [1] L. M. S. Alves et al., Phys. Rev. B \textbf{81, }174532 (2010).