Off-resonant parametric control over THz collective modes in correlated materials: Complex driving protocols, non-equilibrium correlated states and applications.

Currently, light induced states of matter focus the attention of many researchers in condensed matter physics.

An important limitation at the moment is the lack of efficient technology that could be used to control material properties at THz frequencies. On the other hand, this regime is interesting, because many materials exhibit collective resonances in the THz regime.

Some examples are the Higgs modes of superconducting and charge density wave phases, plasmons in two dimensional materials and magnons in antiferromagnets.This project addresses the problem of exciting and manipulating THz collective modes in correlated electronic systems. The idea is to use complex drives with a nontrivial spectral composition, or polarization properties.

One example that will be investigated in this project are amplitude modulated signals. Here, a high frequency signal is modulated on the THz scale. Under special conditions, the modulation can couple to THz collective modes such as magnons and plasmons. The collective modes are then parametrically excited.

An intriguing aspect of this scheme is that the driving is off-resonant, i.e. the driving consists of frequencies which are much higher (e.g. by a factor of a hundred) then the collective resonances.

This can be useful to reduce noise and heating.During this project, we will study ways to off-resonantly excite low frequency collective modes through complex driving protocols.

Our main focus will be on antiferromagnetic Mott insulators with a strong Hund coupling, and plasmons in two dimensional gapped Dirac materials.

Upon establishing tailored driving protocols, we will study the non-equilibrium states to which the systems evolve under strong driving.

Finally, applications, such as time varying spintronic and plasmonic media with unusual wave propagation properties, and means to create THz entangled magnons, which could be useful in quantum devices, will be considered.