Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 41: Quantum-Critical Phenomena (joint session TT/DY)

TT 41.9: Talk

Thursday, March 20, 2025, 11:45–12:00, H31

Examination of the antiferromagnetic superradiant intermediate phase and the effects of geometrical frustration in the Dicke-Ising model — •Jonas Leibig, Anja Langheld, Andreas Schellenberger, and Kai Phillip Schmidt — Chair for Theoretical Physics V, FAU Erlangen-Nürnberg, Germany

We map the Dicke-Ising model to a self-consistent matter Hamiltonian in the thermodynamic limit [1, 2] and solve it using a variety of methods, including exact diagonalization, perturbative and numerical linked-cluster expansions, and density matrix renormalization group. In one dimension, we explore the intermediate phase in the antiferromagnetic model and the multi-critical point in the ferromagnetic model, comparing our results with complementary quantum Monte Carlo simulations [2]. Additionally, we investigate the antiferromagnetic model on the frustrated geometry of the sawtooth chain. We employ high-order series expansions in the strong coupling limit, where the mapping to the self-consistent matter Hamiltonian is definitively valid. Independently, we analyze in greater detail whether the mapping also holds in the specific regime emerging from the frustrated Ising limit induced by an infinitesimal light-matter perturbation.

[1] K. Lenk, J. Li, P. Werner, M. Eckstein, arXiv:2205.05559;

[2] A. Langheld, M. Hörmann, K. P. Schmidt, arXiv:2409.15082.

Keywords: Light-Matter Interaction; Quantum Phase Transition; Series expansion; Numerical linked-cluster expansion; Frustration