P8: Cavity control of the spin-Peierls phase

• Applicant: Professor Dr. Daniele Fausti
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 531215165

The research proposed here aims at leveraging the interaction between electromagnetic fields and matter to control the onset temperature of spin Peierls phase in quasi-1Dimenasional spin ½ systems, CuGeO3 and TiOCl embedded in resonant optical cavities. The hypothesis leading the proposed research project is that the resonant coupling between phonon-magnon excitations and a resonant optical cavity can lead to a renormalization of the Spin Peierls’ transition critical temperature. The overarching aim of P8 is the identification of the optimal condition in terms of cavity resonance and driving field parameters which enable the effective manipulation of orbital and magnetic order in one dimensional anti-ferromagnetic systems. In close collaboration with another project, with input on specific points from other projects, we will study how the presence of weak and strong coupling between materials and optical cavities resonant to phonon or magnon IR allowed transition can influence the separation between spin, orbital and charge degrees of freedom, both in stationary condition as well as in presence of an ultrashort pump resonant to vibrational or magnetic transition (mid-IR and THz). The research program will proceed on by: i) the design, development and commissioning of an experimental setup consisting of tunable cryogenic Fabry-Perot cavity with a large angle optical access and containing a thin slab of material; ii) the Experimental study of the temperature dependence of the THz and mid-IR transmittivity of the phonon-magnon polaritons formed in case studies for 1-dimensional antiferromagnet TiOCl and CuGeO3 embedded into resonant optical cavities; iii) the measurements of the non-equilibrium response of phonon-magnon polaritons in TiOCl and CuGeO3 following the resonant excitation of low energy modes and high energy orbital transitions. Overall the activity proposed aim at demonstrating that the resonant coupling between a material and a resonant cavity can lead to a renormalization of the spin-Peierls transition temperature.

• DFG Programme: Research Units
• Subproject of: FOR 5750: Optical Control of Quantum Materials (OPTIMAL)
• Co-Investigator: Dr. Angela Montanaro