  The Jahn-Teller distortion, by its very nature, is often at the heart of the
various electronic properties displayed by perovskites and related materials.
Despite the Jahn-Teller mode being non- polar in nature, we devise and
demonstrate in the present letter an electric field control of Jahn-Teller
distortions in bulk perovskites. The electric field control is enabled through
an anharmonic lattice mode coupling between the Jahn-Teller distortion and a
polar mode. We confirm this coupling, and explicitly an electric field effect,
through first principles calculations. The coupling will always exist within
the P b2 1 m space group, which is found to be the favoured ground state for
various perovskites under sufficient tensile epitaxial strain. Intriguingly,
the calculations reveal that this mechanism is not only restricted to
Jahn-Teller active systems, promising a general route to tune or induce novel
electronic functionality in perovskites as a whole.
