Quantum fluctuations in incipient ferroelectrics and quantum paraelectrics


Anomalous increase of the dielectric permittivity observed on cooling in incipient ferroelectrics was explained by polar phonon softening and its saturation at low temperatures due to quantum fluctuations. It was observed in SrTiO3, KTaO3 a EuTiO3.. Currently we investigate the soft phonon behaviour in TiO2 and (Eu,Ba,Sr)TiO3. In the latter case, we try to observe the ferroelectric and magnetic quantum critical points, which were recently theoretically predicted. For this purpose we studied the dielectric and magnetic properties down to 0.3 K. We also investigated incipient ferroelectric behavior of water confined in structural nanochannels of the beryl crystal and continue in this type of investigation with water molecules in nanochannels of the cordierite. We also investigate the influence of dc and ac electric fields on the low-temperature dielectric response of incipient ferroelectrics properties and on quantum fluctuations.

Water molecules in nano-sized cages of beryl
Schematic view of water molecules in nano-sized cages of the beryl crystal lattice.

[1] S. Kamba et al., Magnetodielectric effect and optic soft mode behaviour in quantum paraelectric EuTiO3 ceramics, Europhys. Lett. 80, 27002 (2007).

[2] V. Skoromets et al., Ferroelectric phase transition in polycrystalline KTaO3 thin film revealed by terahetrz spectroscopy. Appl. Phys. Lett. 99, 052908 (2011).

[3] S. Glinšek et al., Lattice dynamics and broad-band dielectric properties of the KTaO3 ceramics, J. Appl. Phys. 111, 104101 (2012).

[4] B. Gorshunov et al., Incipient ferroelectricity of water molecules confined to nano-channels of beryl, Nat. Commun. 7 12842 (2016).

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