Lamellar fluctuations melt ferroelectricity
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Fecha
2023
Tipo
artículo preliminar
Autores
Guzmán Verri, Gian Giacomo
Liang, Charles H.
Littlewood, Peter B.
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We consider a standard Ginzburg-Landau model of a ferroelectric whose electrical polarization
is coupled to gradients of elastic strain [1–4]. 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 state with spontaneously broken inversion symmetry [5–10]. Here,
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 SrTiO3 and
KTaO3, 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.
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