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Q: Fachverband Quantenoptik und Photonik

Q 28: Poster – Quantum Optics

Q 28.18: Poster

Tuesday, March 3, 2026, 17:00–19:00, Philo 2. OG

Spatially-varying spin-photon coupling in the antiferromagnetic Dicke-Ising model — •Anja Langheld and Kai Phillip Schmidt — Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg

The Dicke-Ising model is a paradigmatic model for studying light-matter interactions. For antiferromagnetic Ising interactions, the model reveals a rich quantum phase diagram, including a phase with coexisting antiferromagnetic and superradiant order. However, this phase was found to be notably restricted in its extent, in particular in one dimension [1]. As a potential mechanism to expand this phase, we study spatially-varying spin-photon couplings in the Dicke-Ising model beyond the long-wavelength approximation. For this, we employ a specialized quantum Monte Carlo (QMC) method tailored to Dicke-Spin systems [1], allowing us to accurately pinpoint all quantum phase transitions.

[1] A. Langheld et al., Phys. Rev. B 112, L161123 (2025)

Keywords: Light-matter interactions; Quantum Monte Carlo; Quantum phase diagram; Ising model; Dicke model