Sebastian Maehrlein, leader of the “THz Structural Dynamics” group, has been awarded an independent Emmy Noether group by the German Research Foundation (DFG) for a funding period of 6 years. His research focus will be centered on actively steering lattice angular momentum in solids for ultrafast control of material properties.
Even though exchange of energy and linear momentum between lattice vibrations (phonons) and other degrees of freedom is a cornerstone of solid-state physics, phonon angular momentum is commonly just assumed to account for angular momentum conservation but its active control remains elusive. In this long-term project Sebastian F. Maehrlein and his team will prepare and coherently control phonon states with angular momentum to study and actively manipulate coupled electronic and spin degrees of freedoms. As a first step, the group will work towards polarization tailoring of highly intense few-cycle pulses in the THz and multi-THz (mid-infrared) spectral range. Once this control is established, the preparation and detection of circularly polarized (degenerate chiral) coherent phonons in benchmark materials will be tackled. The coupling of this coherent phonon angular momentum to ordered spin states in magnetic materials or atomically thin semiconductors bears a number of fundamental scientific questions and application potential. Eventually, the team aims to establish phonon angular momentum as a novel ultrafast tuning knob for comprehensive material control.