Metal-insulator transition and superconductivity in the Mott insulator GaTa$_{4}$Se$_{8}$ : towards a tuning of the Mott transition by electric pulses

We have recently discovered the existence of a non-volatile electric-pulse-induced resistive switching (EPI-RS) in the spinel Mott insulator GaTa$_{4}$Se$_{8}$ [1]. The origin of this effect is different from other EPI-RS mechanisms identified to date [2]. A granular superconducting state below $T_{C}$ = 5-7 K, ascertained by critical current and critical field data obtained on single crystals, appears in the EPI ``metallic'' state. This transition is reminiscent of the bulk superconductivity at 5-8 K obtained under pressure [3]. Interestingly, STM experiments have revealed a puzzling electromechanical coupling between the tip voltage and the GaTa$_{4}$Se$_{8}$ sample surface. All these results may therefore indicate that, beside electronic doping and pressure, electric pulses, through an electrostrictive effect, could be a relevant parameter to tune the Mott metal-insulator transition. [1] C. Vaju \textit{et al.}, Adv. Mater. 20, 2760 (2008) [2] R. Waser, M. Aono, Nature Mat. 6, 833 (2007) [3] M.M. Abd-Elmeguid \textit{et al.}, PRL 93, 126403 (2004)