Future solid-state devices will have to be multifunctional, highly manipulable and display quantum mechanical effects that surpass the classical properties of state-of-the-art devices. Their properties are usually controlled by statically modifying the composition and structure of their constituent atoms or their environment with pressure and electromagnetic fields. Our research group takes a fundamentally different approach, by investigating theoretically and computationally how properties of solids change dynamically, when the atoms are collectively excited. Below, you find a list of topics of current interest to the group.
For an introduction to the theory of coherent phonons and nonlinear phononics, please check out my recent 4-hour lecture series from the Nordita Winter School 2023. The entire winter school can be found here.
Shaken, not strained: How to control electronic order with lattice vibrations
Optical phonons, collective vibrational excitations of atoms,
present a unique opportunity to modify solid-state interactions
that are inherently dependent on the distance between atoms
with low excitation energies in the terahertz and mid-infrared
spectral range, while leaving the electronic system in its
ground state. Ultrashort terahertz pulses can resonantly excite
phonons, inducing atomic vibrations with large amplitudes.
The vibrational dynamics of the solid are governed by
nonlinear interactions between phonons and other degrees of
freedom under which the electronic correlations in the solid change.
Producing magnetism with motion
Optical control of magnetic order is promising magnetic data processing and storage that operates on timescales of pico- and femtoseconds, orders of magnitude faster than established technology. Coherent optical phonons would provide an alternative route to magnetic-order control operating at low excitation energies in the terahertz spectral range. Rotational motions of ions, such as in circularly polarized or chiral phonons, act as atomistic electromagnetic coils and produce dynamical magnetic fields that interact with electronic angular momentum.
Strongly coupled light: Cavity dynamics
When quasiparticles in a solid couple to electromagnetic modes constrained by an optical cavity, the light-matter interaction strength can be tremendously enhanced. We utilize concepts from the field of strong light-matter interactions to enhance resonant processes of energy redistribution between highly vibrationally excited states and other bosonic excitations in solids. This allows us to direct the flow of energy in the system and to enhance the mechanisms of coherent control over the ordered phases corresponding to these excitations.