Quantum paraelectricity

Quantum paraelectricity[1] is a type of incipient ferroelectricity where the onset of ferroelectric order is suppressed by quantum fluctuations.

In this case the soft-mode frequency never becomes unstable (Fig.

Experimentally this is associated with an anomalous behaviour of the dielectric susceptibility, for example in SrTiO3.

[4] In a normal ferroelectric, close to the onset of the phase transition the dielectric susceptibility diverges as the temperature approaches the Curie temperature.

However, in the case of a quantum paraelectric the dielectric susceptibility diverges until it reaches a temperature low enough for quantum effects to cancel out the ferroelectricity (Fig.

a) Ferroelectric soft-mode frequency as a function of temperature. The dashed lines shows the behaviour of a regular ferroelectric material with a ferroelectric instability at the Curie temperature. The solid lines shows the quantum paraelectric frequency with quantum fluctuations preventing a ferroelectric instability from arising. b) The dashed line shows the divergence of the dielectric susceptibility near the Curie temperature for a regular ferroelectric. The solid line indicates the anomalous behaviour of a quantum paraelectric where the dielectric susceptibility begins to diverge in the regular manner but levels off.