V Laboratory
Department of Physics
Nagoya University
Furocho, Chikusa, Nagoya

Nonlinear conduction in Ca2RuO4

In correlated insulating phases such as the Mott insulating or charge-order state, electrons repel each other owing to the strong Coulomb interaction. Such an insulating state can be regarded as an "electron ice", in which each electron is localized on each site. This "electron ice" is melted into a conductive state not only with heating but also by a flow of electrons. The resultant conductive state realized by applying electric field or current is highly non-equilibrium, which should be distinguished with the conductive state realized by heating, but its nature is far from understandings. Here we show such a non-equilibrium electronic state in the Mott insulator Ca2RuO4. We find an intrinsic nonlinear conduction phenomenon in this material by using a proper temperature evaluation method with a non-contact infrared thermometer. We propose a novel gap suppression induced by current as an origin of the observed nonlinearity, which has also been discussed in superconducting or charge-ordered state under external current, implying a ubiquitous nature in non-equilibrium electronic state.

"Current-Induced Gap Suppression in the Mott Insulator Ca2RuO4"
by Ryuji Okazaki, Yasuo Nishina, Yukio Yasui, Fumihiko Nakamura, Takashi Suzuki, Ichiro Terasaki
J. Phys. Soc. Jpn. 82 (2013) 103702.

(Figure) Nonlinear conduction in Ca2RuO4