Quantum Effects of Phase Transitions in Ferroelectric Crystals—Experiments and Models

Abstract

From structural data obtained experimentally, some microscopic parameters can be estimated unambiguously. By using these parameters, a quantum Ising model can explain the isotope effect in SrTiO ₃ and KH ₂ PO ₄ . The ferroelectric transition in ¹⁸ O isotope crystal of SrTiO ₃ is successfully explained only by a mass effect in quantum state, which demonstrates importance of quantum effects in ferroelectrics.

Keywords:

• Isotope effect
• SrTiO₃
• KH₂PO₄
• structure parameters
• quantum Ising model
• quasi-harmonic model
• quantum paraelectricity
• Barrett's relation
• phase diagram