Quantum paraelectricity
[See ] is a type of incipient
ferroelectricity
Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoelectric and pyroelectric, with the a ...
where the onset of ferroelectric order is suppressed by quantum fluctuations.
[See ] From the soft mode theory of ferroelectricity,
[See ] this occurs when a ferroelectric instability is stabilized by
quantum fluctuations
In quantum physics, a quantum fluctuation (also known as a vacuum state fluctuation or vacuum fluctuation) is the temporary random change in the amount of energy in a point in space, as prescribed by Werner Heisenberg's uncertainty principle. ...
. In this case the soft-mode frequency never becomes unstable (Fig. 1a) as opposed to a regular ferroelectric.

Experimentally this is associated with an anomalous behaviour of the dielectric susceptibility, for example in
SrTiO3.
[See ] In a normal ferroelectric, close to the onset of the phase transition the
dielectric susceptibility diverges as the temperature approaches the
Curie temperature
In physics and materials science, the Curie temperature (''T''C), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism. The Cu ...
. 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. 1b). In the case of
SrTiO3 this is around 4K.
Other known quantum paraelectrics are
KTaO3 and potentially
CaTiO3.
[See ]
References
{{Reflist
Electric and magnetic fields in matter