Abstract
All known proper ferroelectrics are unable to polarize normal to a surface or interface if the resulting depolarization field is unscreened, but there is no fundamental principle that enforces this behavior. In this work, we introduce hyperferroelectrics, a new class of proper ferroelectrics which polarize even when the depolarization field is unscreened, this condition being equivalent to instability of a longitudinal optic mode in addition to the transverse-optic-mode instability characteristic of proper ferroelectrics. We use first-principles calculations to show that several recently discovered hexagonal ferroelectric semiconductors have this property, and we examine its consequences both in the bulk and in a superlattice geometry.
- Received 25 November 2013
DOI:https://doi.org/10.1103/PhysRevLett.112.127601
© 2014 American Physical Society
Viewpoint
Polarization that Holds Steady
Published 26 March 2014
A predicted class of materials called hyperferroelectrics could prove more stable against the depolarizing internal electric fields known to impede ferroelectricity in thin films.
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