Ultrafast generation, propagation and detection of chiral phonons

• Applicant: Professor Dr. Tobias Kampfrath
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 541503763

The central goal of this project is to implement and study the generation, propagation and detection of chiral phonons (i.e., phonon angular momentum) in generic spintronic FM|T|HM or FM|T|FM’ thin-film stacks on their natural (femtosecond) time scale. To this end, phonon angular momentum (PAM) is generated by femtosecond optical excitation of a ferromagnetic metal layer FM with in-plane or out-of-plane magnetization. Consequently, PAM is injected into the adjacent electrically insulating transmission layer T. Finally, PAM reaches the heavy-metal layer HM, where it can be detected by conversion into an in-plane charge current that emits a measurable terahertz electric field. To detect out-of-plane PAM, we replace HM by another ferromagnetic-metal layer FM’ where the arriving phonon angular momentum is measured magneto-optically by the torque it exerts on the magnetization of FM’. Using this platform, we aim to gain insight into the ultrafast dynamics of PAM generation in FM, the propagation through T (in terms of, e.g., dispersion, attenuation, ballistic vs diffusive) and the detection process in HM and FM’.

• DFG Programme: Research Units
• Subproject of: FOR 5844: Chiral phonons for spintronics_ChiPS