Mainz 2026 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 33: Cavity QED, QED, and Spin-Boson Systems I

Q 33.6: Talk

Wednesday, March 4, 2026, 15:45–16:00, P 4

Frustration effects and self-consistent matter description in the Dicke-Ising model on the sawtooth chain — •Jonas Leibig, Max Hörmann, Anja Langheld, Andreas Schellenberger, and Kai Phillip Schmidt — Department of Physics, Staudtstraße 7, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany

We investigate how the exact thermodynamic-limit mapping of the Dicke*Ising model to a self-consistent effective matter Hamiltonian applies to the geometrically frustrated sawtooth chain. The mapping, established in Ref. [2], was recently solved with NLCE+DMRG for the unfrustrated chain in our work [1]. Using the same method, we obtain the zero-temperature phase diagram of the sawtooth geometry and identify frustration-induced features absent in the unfrustrated case. In the frustrated Ising limit, an infinitesimal effective transverse field lifts the classical degeneracy and produces a disorder-by-disorder transition, analogous to the transverse-field Ising model [3].

References

[1] J. Leibig, M. Hörmann, A. Langheld, A. Schellenberger, and K. P. Schmidt, “Quantitative NLCE+DMRG approach for 1D Dicke-Ising models via self-consistent matter Hamiltonians’, to be published (2025).

[2] J. Román-Roche, Á. Gómez-León, F. Luis, and D. Zueco, “Linear response theory for cavity QED materials at arbitrary light–matter coupling strengths”, Physical Review B 111, 035156 (2025).

[3] D. J. Priour, M. P. Gelfand, and S. L. Sondhi, “Disorder from disorder in a strongly frustrated transverse-field Ising chain”, Phys. Rev. B 64, 134424 (2001).

Keywords: Light-Matter Interaction; Quantum Phase Transition; Numerical linked-cluster expansion; Geometrical frustration; Density matrix renormalization group