Rhombohedral distortion in the electronic band structure of strained PbZrTiO3

Perovskite oxides extend in application prospects from electronics to energy conversion and catalysis. Such abundant functionalities are a direct consequence of the rich physics which derives from the interplay of their multiple degrees of freedom. Ferroelectrics in particular are promising to catalysis and energy conversion due to their intrinsic property of efficiently separating the electrons and holes as a requirement to stabilize a well-defined ferroelectric state. Deriving the most fundamental electronic properties as encoded in their experimental band structure is challenging due to their insulating character. Here we record the ferroelectric-dependent three-dimensional electronic structure of ferroelectric PbZrxTi1-xO3 x=0.2 PZT in k-resolved soft X-ray photoelectron spectroscopy (SX-ARPES) experiments. We identify the signature of the rhombohedral distortion which features the low temperature T=12 K phase and we show that it maintains up to the room temperature. The band structure extracted across the whole Brillouin zone reveals on the one hand the immune character of the PZT to oxygen vacancies formation under the X-ray beam - which is a common mechanism of obscuring the intrinsic band structure in ARPES studies of oxides. On the other hand it reveals that the additional charges needed to screen the depolarizing field of the ferroelectric with well-defined FE polarization P+ or P- are either incoherent electrons in the valence band or the carriers (ionized impurities) above the Fermi level, close to the conduction band minimum.