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MO: Fachverband Molekülphysik

MO 14: Polaritonic Effects in Molecular Systems II (joint session MO/Q)

MO 14.4: Talk

Wednesday, March 12, 2025, 11:45–12:00, HS XV

Control of cavity dissipations across the insulator-to-metal transition in 1T-TaS₂ — •Giacomo Jarc¹, Angela Montanaro¹, Shahla Yasmin Mathengattil^2,3, Enrico Rigoni^1,3, and Daniele Fausti¹ — ¹Department of Physics, FAU Erlangen-Nürnberg Erlangen, Germany — ²Department of Physics, Università di Trieste, Trieste, Italy — ³Elettra Sincrotrone, Basovizza (Trieste), Italy

Using optical cavities resonant with material excitations enables controlling light-matter interaction in both the regimes of weak and strong coupling. We study here the coupling of low-energy excitations in the charge-density-wave (CDW) material 1T-TaS₂ across its insulator-to-metal transition when embedded into tetahertz Fabry-Pérot cryogenic cavities. In the dielectric state, we reveal the signatures of a multimode vibro-polariton mixing, with the polariton modes inheriting character from all the CDW phonons as a consequence of the cavity-mediated hybridization. The multimode vibrational strong coupling is suppressed across the insulator-to-metal transition as a consequence of the optical dissipations introduced by the free charges, and a vibrational weak coupling regime is observed in proximity of the phase transition. When the cavity frequency is tuned within the spectral range of the continuum Drude excitation, we reveal that the quality factor of the cavity, which quantifies the dissipations of the coupled system, decreases passing from the insulating to the metallic state. Our evidences points to a scenario in which the free charges can effectively couple to the cavity field and subsequently modify the collective light-matter coupling.

Keywords: Terahertz cavity; Phonon-polaritons; Insulator-to-metal transition; Cavity dissipations; Free charges