Quasi-static elastic domains in the quantum paraelectric phase of SrTiO3

In spite of a long history many electronic and lattice properties of the quantum paraelectric SrTiO3 remain puzzling. Last year we have discovered a novel ingredient that sets its ground state. We found that the softening of the TO mode is accompanied by a large TA softening at a tiny q-vector pointing to the existence of fluctuating domains as wide as 20 nm. Motivated by our results it has been proposed that quantum paraelectrics are driven by a flexo-electric coupling that leads to longrange-ordered modulated phase. Here we apply for five days of experiment on Cristal to study the diffuse scattering associated with this TA softening and its evolution in the ferroelectric phase of SrTiO3 (through the substitution with Ca doping). This result may reveal the presence of an hidden incommensurate transition in the quantum paraelectric phase of SrTiO3.