Lamellar fluctuations melt ferroelectricity

Abstract

We consider a standard Ginzburg-Landau model of a ferroelectric whose electrical polarization is coupled to gradients of elastic strain. At the harmonic level, such flexoelectric interaction is known to hybridize acoustic and optic phonon modes and lead to phases with modulated lattice structures that precede the symmetry broken state for sufficiently large couplings. Here, we use the we use the self-consistent phonon approximation to calculate the effects of thermal and quantum polarization fluctuations on the bare modes to show that such long-range modulated order is unstable at all temperatures. We discuss the implications for the nearly ferroelectric SrTiO${}_3$ and KTaO${}_3$, and propose that these systems are melted versions of an underlying modulated state which is dominated by non-zero momentum thermal fluctuations except at the very lowest temperatures.

17 pages, 3 figures, 1 table, supplementary information included

References in corpus (7)

• Giant strain gradient elasticity in SrTiO3 membranes: bending versus stretching
• The effects of intrinsic local distortions vs. dynamic thermal motions on the stability and band gaps of cubic oxide and halide perovskites
• Order-Disorder Ferroelectric Transition of Strained SrTiO3
• The quantum paraelectric phase of SrTiO${}_3$ from first principles
• Quantum Critical Paraelectrics and the Casimir Effect in Time
• Intrinsic local symmetry-breaking in nominally cubic paraelectric BaTiO3
• Mesoscopic tunneling in strontium titanate

Cited by in corpus (2)

• Spin-dependent anisotropic electron-phonon coupling in KTaO${}_3$
• Nanoscale Polar Landscapes in Quantum Paraelectric SrTiO3