The invited talk was delivered on 17th September, at the EMRS Fall Meeting 2018, Warsaw.
Symposium P: Epitaxial oxide films for electronic applications
Title: “Lattice instabilities and functional properties of oxide perovskites”
The broad family of perovskites hosts an extraordinary range of functional properties. A clue to this astonishing versatility is the capability of perovskites to admit distortions from the ideal cubic structure, which leads to buckling, tilting, rotations or elongations of the octahedral structural units. In turn, these deformations modulate the ionic bonds in the lattice, fine-tuning the physical properties. Here we analyze some of the perovskite lattice instabilities and their interaction with electric fields. First we discuss this relation for antiferrodistortive (AFD) octahedral rotations and polar modes occurring in LaAlO3/SrTiO3 quantum wells (QWs) . With some exceptions, these two order parameters rarely coexist in a bulk crystal. Interestingly, in the particular case of LaAlO3/SrTiO3 QWs, their competition leads to structural changes concomitant with a metal-insulator transition. Secondly, we discuss the role of a previously unreported antiferroelectric (AFE) mode in the dielectric properties of the canonical SrTiO3 perovskite . In particular, we show that such properties can dominate the response of ferroelastic domains to external electric biases, overruling the response from polar domain walls. These observations illustrate how sensitive perovskite are to lattice distortions and provide insights towards nanoscale control of material properties.  Gazquez et al., Phys. Rev. Lett. 119, 106102 (2017) ;  B. Casals et al., Phys. Rev. Lett., in press