Coexistence Of Polar Distortion And Metallicity In Pbti(1-X)Nbxo(3)

Ferroelectricity has been believed unable to coexist with metallicity since the free carriers can screen the internal Coulomb interactions of dipoles. Very recently, one kind of material called ferroelectric metal was reexamined. Here, we report the coexistence of metallicity and polar distortion in a candidate for ferroelectric metal PbTi1-x NbxO3 via doping engineering. The ferroelectriclike polar distortion in all the doped PbTi1-x NbxO3, with x ranging from 0.04 to 0.12, was observed by the piezoresponse force microscopy and the scanning transmission electron microscopy measurements. PbTi1-x NbxO3 films become more conductive with more doping density, and a metallic behavior emerges when x reaches 0.12. Our first-principles calculations further revealed that the doped Nb ions in the films can only provide free electrons, but are not able to damage the dipoles in unit cells even with the heaviest doping density of 0.12. We believe that these results confirm a feasibility of realizing the coexistence of metallicity and polar distortion for other ferroelectrics in a common way, and motivate the synthesis of some new materials with artificially designed properties even incompatible in nature.