Effect of quantum fluctuations on structural phase transitions inSrTiO3andBaTiO3

Abstract

Using path-integral Monte Carlo simulations and an ab initio effective Hamiltonian, we study the effects of quantum fluctuations on structural phase transitions in the cubic perovskite compounds ${\mathrm{SrTiO}}_3$ and ${\mathrm{BaTiO}}_3$. We find quantum fluctuations affect ferroelectric (FE) transitions more strongly than antiferrodistortive (AFD) ones, even though the effective mass of a single FE local mode is larger. For ${\mathrm{SrTiO}}_3$ we find that the quantum fluctuations suppress the FE transition completely, and reduce the AFD transition temperature from 130 to 110 K. For ${\mathrm{BaTiO}}_3$, quantum fluctuations do not affect the order of the transition, but do reduce the transition temperature by 35–50 K. The implications of the calculations are discussed. © 1996 The American Physical Society.