Dynamical Multiferroicity

A static spin-spiral in space can, via the Dzyaloshiksii-Moriya interaction lead to an effective polarisation; by exploiting the duality between electricity and magnetism in Maxwell’s equations, a complementary effect – Dynamical Multiferroicity – is possible.

In dynamical multiferroicity, a magenetic moment results from electric dipoles with transverse (rotational) motion:

    \[ \mathbf{m} = \lambda \mathbf{p}\times \partial_t \mathbf{p} \]

Dynamical multiferroicity may be either externally induced, e.g.: by excitation with a circularly polarised laser, or inherent. This latter case may occur in a paraelectric material where the net polarisation is zero, but induced magnetic signatures of dynamical multiferroicity may be present due to transverse fluctuations of electric dipoles. Quantum paraelectrics, including strontium titanate, where quantum fluctuations prevent the appearance of ferroelectric order, are prime candidate materials.

Seminal paper:
Dynamical Multiferroicity
Dominik Maximilian Juraschek, Michael Fechner, Alexander V. Balatsky, Nicola Ann Spaldin
Phys. Rev. Materials 1, 014401 (2017)

Other key papers:
Dynamic multiferroicity of a ferroelectric quantum critical point
K. Dunnett, J.-X. Zhu, N. A. Spaldin, V. Juricic, A. V. Balatsky
Physical Review Letters. 122. 057208 (2019)