Ferroelectric control of a Mott insulator

The electric field control of functional properties is an important goal in oxide-based electronics. To endow devices with memory, ferroelectric gating is interesting, but usually weak compared to volatile electrolyte gating. Here, we report a very large ferroelectric field-effect in perovskite heterostructures combining the Mott insulator CaMnO 3 and the ferroelectric BiFeO 3 in its “supertetragonal” phase. Upon polarization reversal of the BiFeO 3 gate, the CaMnO 3 channel resistance shows a fourfold variation around room temperature and a tenfold change at ~200 K. This is accompanied by a carrier density modulation exceeding one order of magnitude. We have analyzed the results for various CaMnO 3 thicknesses and explain them by the electrostatic doping of the CaMnO 3 layer and the presence of a fixed dipole at the CaMnO 3 /BiFeO 3 interface. Our results suggest the relevance of ferroelectric gates to control orbital- or spin-ordered phases, ubiquitous in Mott systems and pave the way toward efficient Mott-tronics devices.