Magnetophononics: ultrafast spin control through the lattice*

The interplay between the electronic properties and crystal structure dictates the functional properties of materials. In this talk, I will discuss how one can use the selective excitation of phonons with light as a perturbative method to manipulate the magnetic properties of insulators. I will first introduce the general theoretical concept of phonon excitation towards the non-linear regime, also known as non-linear phononics [1], and its possible side effects onto crystal and electronic structure. In the following, I will present in detail two case studies which utilize this approach in magnetic materials.
I first will discuss the coherent modulation of the electric polarisation, which creates a magnetization even in materials with no existing spin structure [2]. This transient state of broken space and partiy odd symmetry is multiferroic and comprises unexpected outcomes like a phonon Zeeman effect and magnon excitation [3]. As a second example, I show how the phonon excitation and its related structural distortion modulates magnetic exchange interactions. For the specific case of Cr₂O₃, the right tuning of induced deformations [4] allows modulating the magnetic spin arrangement, which generates a new magnetic state. I will also speculate about where the field is going and provide my own perspectives.

[1] M. Först, et al., Nature Phys. 7, 854 (2011).
[2] D. M. Juraschek, et al., Phys. Rev. Mat. 1, 014401 (2017).
[3] T. F. Nova, et al. , Nature Phys. 13, 132 (2016).
[4] M. Fechner, et al., arXiv 1707.03216, (2017).