Can free charge carriers enhance polarization?

Ferroelectricity and metallicity has long been thought to be mutually exclusive because of the screening of the long range coulomb force. After the observation of ferroelectric-like transitions in metals recently, there has been a surge of interest in the study of `ferroelectric metals’ and the stabilizing forces of structural polarization therein. Nevertheless, addition of carriers to semiconducting or insulating ferroelectrics is still usually thought to be detrimental to ferroelectricity. In this talk we show, by using first principles calculations, that ferroelectric polarization can actually be strengthened by introduction of free carriers in a series of oxide ferroelectrics. We consider introduction of carriers through electrostatic gating, which can alter the carrier concentration without changing the level of disorder.