Dr Kyohei Takae

University of Tokyo

Shape controls polarisation: Ferroelectricity and antiferroelectricity in dipolar crystals formed by shape-anisotropic particles

Fluids and Materials Seminar

18th June 2018, 2:00 pm – 3:00 pm

Ferroelectricity and antiferroelectricity are widely seen in various
types of condensed matter
and are of technological significance not only due to their electrical
but also due to intriguing cross-coupling effects such as
electro-mechanical effects.
The control of the two types of polarisation ordering has practically
been made
by changing the ionic radius of a constituent atom or externally
applying strain for inorganic crystals
and by changing the shape of a molecule for organic crystals.
However, the basic physical principle behind such controllability
involving structural organization is still unknown.
On the basis of a physical picture that a competition of dipolar order
with another type of order is essential to understand this phenomenon,
here we develop a simple model system composed of spheroidal particles
with a permanent dipole.
In this model, we reveal that energetic frustration between
the two types of anisotropic interactions, dipolar and steric interactions,
is a key to control not only the phase transition but also the coupling
between polarisation and strain.
Our finding provides a fundamental physical principle for
self-organization to a crystal with
desired dipolar order and realisation of large electro-mechanical effects.

Organiser: Rachel Bennett

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