Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 79: Plasmonics and nanooptics: Light-matter interaction, spectroscopy III
O 79.1: Talk
Thursday, March 12, 2026, 10:30–10:45, HSZ/0403
Cavity control of multiferroic order in the single-layer NiI2 — •Chongxiao Fan1,2, Emil Viñas Boström1, Xinle Cheng1, Lukas Grunwald1, Dante Kennes2, and Angel Rubio1,3 — 1Max Planck Institute for the Structure and Dynamics of Matter — 2Institute for Theory of Statistical Physics, RWTH Aachen University — 3Initiative for Computational Catalysis, Flatiron Institute
Controlling materials in thermal equilibrium, through their interactions with quantum fluctuations of the electromagnetic field, is a promising new frontier in material engineering. Although recent experiments have demonstrated cavity effects in charge density wave, quantum Hall systems and superconducting systems, a smoking gun experiment is lacking for magnetic systems. To a large extent this comes from the focus on discontinuous phase transitions (e.g. from antiferro- to ferromagnetic), where a large light-matter coupling is required for cavity modifications to be observable. Here, we instead propose spiral magnets as a promising platform to explore cavity effects, where even a small cavity-mediated change in magnetic interactions is directly reflected in a change of the spiral wavelength. For concreteness we focus on the single-layer multiferroics NiI2 and NiBr2, with the surface phonon polaritons of the paraelectric substrate SrTiO3 acting as the cavity. We show that the surface cavity suppresses the ratio J3/J1 of the third nearest and next nearest neighbor exchange interactions, leading to a increase of the spiral wavelength and the eventual transition into a ferromagnetic state. Our work proposes a realistic platform to observe cavity renormalization effects in magnetic systems.
Keywords: Light-matter interaction; Surface Cavity; Multiferroics; Phase transition; 2D materials