Ambipolar gate effect and low temperature magnetoresistance of ultrathin La0.8Ca0.2MnO3 Films

Ultrathin La0.8Ca0.2MnO3 films have been measured in a field-effect geometry. The electric field due to the gate produces a large ambipolar decrease in resistance at low temperatures. This is attributed to the development of a pseudogap in the density of states and the couple of localized charge to strain. The gate effect and mangetoresistance are interpreted in a consistent framework. The implications for the low temperature behavior of a manganite film in the two dimensional limit are discussed.