Title: Current-induced giant diamagnetism and Mott semimetal behavior in Ca2RuO4

Speaker: Dr. Chanchal Sow, Kyoto University, Japan

Abstract: Ordinary insulators do not contain conduction electrons. In contrast, the Mott insulator contains conduction electrons but are immobile, or “frozen” due to the strong coulomb repulsion among them. With some external stimuli, such as chemical substitution or pressure, the frozen electrons in the Mott insulator may melt and start to flow. It is well known that as the electrons begin to flow they exhibit remarkable properties such as high-temperature superconductivity, metal-insulator transition, and colossal-magnetoresistance.

I will be discussing about the effect of DC current, which turns out to be another unique and powerful stimulus for the Mott insulators. Under DC current, the insulating nature of a Mott insulator Ca2RuO4 is strongly suppressed and eventually becomes a semimetal-like state. The antiferromagnetic ground state is completely suppressed by just 1 A/cm2 current. More importantly, we find “giant diamagnetism” below 50 K. The size of the diamagnetism is largest among any other existing non-superconducting diamagnetic materials. We also find that the diamagnetism instantly vanishes by switching off the current. In my talk, I will be discussing about the discovery of “giant diamagnetism” and its possible origins.