Spectroscopy of Supersolids in Toroidal Traps

• Applicant: Professor Dr. Tilman Pfau
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 570946760

A supersolid is a famous example of self-organized structures in quantum fluids, which was recently observed in our group. One can think of this state of matter as a quantum mechanical superposition of two very different states of matter - a superfluid on the one side and a solid with a periodic structure on the other side. Due to the symmetry breaking upon formation of such a collective quantum state and the corresponding spatial structures two different kinds of sound are present in this state of matter. In addition, also the famous Higgs mode appears, which in contrast to the phonons has a finite effective mass. Experiment studies so far were mostly done in harmonic traps which complicate the observation of these modes as the confinement mutually couples all these modes. In this project we will observe the Higgs amplitude mode alongside the sound-like phonons in a dipolar supersolid in a toroidal geometry. Due to the effective periodic boundary conditions the excitations are predicted to appear essentially decoupled in their pure form. In a close collaboration between experiment and theory (University of Lund, Sweden) we will also study undamped and therefore persistent currents in a torus supersolid, which is a clear hallmark of superfluidity despite the modulated density.

• DFG Programme: Research Grants
• International Connection: Sweden
• Major Instrumentation: frequency doubled vexel laser at 421 nm
• Instrumentation Group: 5730 Spezielle Laser und -Stabilisierungsgeräte (Frequenz, Mode)
• Co-Investigator: Dr. Ralf Klemt
• Cooperation Partner: Professorin Dr. Stephanie M. Reimann