Structural and metal-insulator transitions in ionic liquid-gated Ca3Ru2O7 surface

Abstract

We report the fabrication and measurements of ionic liquid gated Hall bar devices prepared on thin Ca$_3$Ru$_2$O$_7$ flakes exfoliated from bulk single crystals that were grown by a floating zone method. Two types of devices with their electrical transport properties dominated by $c$-axis transport in Type A or that of the in-plane in Type B devices, were prepared. Bulk physical phenomena, including a magnetic transition near 56 K, a structural and metal-insulator transition at a slightly lower temperature, as well as the emergence of a highly unusual metallic state as the temperature is further lowered, were found in both types of devices. However, the Shubnikov-de Haas oscillations were found in Type A but not Type B devices, most likely due to enhanced disorder on the flake surface. Finally, the ionic liquid gating of a Type B device revealed a shift in critical temperature of the structural and metal-insulator transitions, suggesting that such transitions can be tuned by the electric field effect.