Electrostatic carrier doping to perovskite transition-metal oxides

Minute variations in a carrier density can drive drastic qualitative changes in the ground state of a correlated electron system. To establish methods of critical control of the carrier density at the boundary of phase competitions is a pressing challenge in an interdisciplinary field of modern condensed-matter physics and semiconductor technologies. Employing the technique of electrostatic charging is widely believed to enable continuous tuning in the same material with minimum disturbance of the underlying lattice. We focus here on the perovskite transition-metal (TM) oxides which are an abundant repository of strong correlation phenomena. Two major approaches are reviewed: one is to use a thin dielectric film deposited on the top of the perovskite TM oxides, the other is to use a dielectric single-crystalline substrate and deposit a thin film of the perovskite TM oxides on top of it. Although the methods have only recently been proposed, one can explore their growing capabilities within this paper.