Valence fluctuations in Sn(Pb)${}_2$P${}_2$S${}_6$ ferroelectrics

Abstract

The valence fluctuations which are related to the charge disproportionation of phosphorous ions $P^{4+}+P^{4+}\to P^{3+}+P^{5+}$ are the origin of ferroelectric and quantum paraelectric states in Sn(Pb)${}_2$P${}_2$S${}_6$ semiconductors. They involve recharging of SnPS${}_3$ or PbPS${}_3$ structural groups which could be represented as half-filled sites in the crystal lattice. Temperature-pressure phase diagram for Sn${}_2$P${}_2$S${}_6$ compound and temperature-composition phase diagram for (Pb${}_y$Sn${}_{1-y}$)${}_2$P${}_2$S${}_6$ mixed crystals, which include tricritical points and where a temperature of phase transitions decrease to 0 K, together with the data about some softening of low energy optic phonons and rise of dielectric susceptibility at cooling in quantum paraelectric state of Pb${}_2$P${}_2$S${}_6$, are analyzed by GGA electron and phonon calculations and compared with electronic correlations models. The anharmonic quantum oscillators model is developed for description of phase diagrams and temperature dependence of dielectric susceptibility.

References in corpus (13)

• Quantum criticality in ferroelectrics
• From band insulator to Mott insulator in one dimension
• Theory of Electronic Ferroelectricity
• Linear and nonlinear optical characteristics of the Falicov-Kimball model
• Exact Bond Ordered Ground State for the Transition Between the Band and the Mott Insulator
• Theory of Valence Transition in BiNiO${}_3$
• Nature of the Peierls- to Mott-insulator transition in 1D
• Theory of Charge Kondo Effect on Pair Hopping Mechanism
• Observation of Kibble-Zurek behavior near the Lifshitz point in ferroelectrics with incommensurate phase
• Neutron scattering study of ferroelectric Sn2P2S6 under pressure
• Electric Dipolar Kondo Effect Emerging from Vibrating Magnetic Ion
• Electric Dipolar Susceptibility of the Anderson-Holstein Model
• Phonon-like excitations in the two-state Bose-Hubbard model

Cited by in corpus (7)

• Nonlinear dynamics of ferroelectrics with three-well local potential
• Double hysteresis loops in proper uniaxial ferroelectrics
• Phase diagram of ferroelectrics with tricritical and Lifshitz points at coupling between polar and antipolar fluctuations
• Quantum paraelectric state and critical behavior in Sn(Pb)${}_2$P${}_2$S(Se)${}_6$ ferroelectrics
• Description of lattice anharmonicity observed in ferroelectrics with unusual three-well local potential
• Slow and fast relaxation times of quantum lattice model with local multi-well potentials: phenomenological dynamics for Sn${}_2$P${}_2$S${}_6$ ferroelectric crystals
• Description of CuInP${}_2$S${}_6$ ferrielectrics in a mixed Ising model