title: Ultrafast Structure Switching through Nonlinear Phononics.
abstract: We describe a mechanism by which nonlinear phononics allows ultrafast coherent and directional control of transient structural distortions. With ErFeO_{3} as a model system, we use density functional theory to calculate the structural properties as input into an anharmonic phonon model that describes the response of the system to a pulsed optical excitation. We find that the trilinear coupling of two orthogonal infrared-active phonons to a Raman-active phonon causes a transient distortion of the lattice. In contrast to the quadratic-linear coupling that has been previously explored, the direction of the distortion is determined by the polarization of the exciting light, introducing a novel mechanism for nonlinear phononic switching. Since the occurrence of the coupling is determined by the symmetry of the system we propose that it is a universal feature of orthorhombic and tetragonal perovskites.
authors.affiliation: Materials Theory, ETH Zurich, CH-8093 Zürich, Switzerland.
authors.forename: D M
authors.initials: DM
authors.lastname: Juraschek
authors.affiliation: Materials Theory, ETH Zurich, CH-8093 Zürich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Fechner
authors.affiliation: Materials Theory, ETH Zurich, CH-8093 Zürich, Switzerland.
authors.forename: N A
authors.initials: NA
authors.lastname: Spaldin