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THU: Thursday Contributed Sessions

THU 8: Frustrated Quantum Systems: Contributed Session to Symposium

THU 8.4: Talk

Thursday, September 11, 2025, 15:00–15:15, ZHG009

Control of the carrier distribution in a quasi-2D Mott-Hubbard solid via ultrafast photodoping and pressure-tuning revealed by terahertz-infrared spectroscopy — Konstantin Warawa¹, Yassine Agarmani¹, Sheng Qu¹, Harald Schubert¹, Martin Dressel², Michael Lang¹, Hartmut G. Roskos¹, and •Mark D. Thomson¹ — ¹Physikalisches Institut, J. W. Goethe-Universität, 60438 Frankfurt am Main, Germany — ²1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany

Electronic correlations in solids can yield a rich phase diagram including a Mott metal-insulator transition (MIT), superconductivity and magnetic order, not only due to the interplay between bandwidth (W) and Coulomb repulsion (U), but also the concerted response of the band structure to charge-carrier excitation. This can lead to drastic effects in Mott-Hubbard insulators with small energy gaps (Δ of some 10 meV), such as the organic charge-transfer salt presented here, κ-(BEDT-TTF)₂Cu[N(CN)₂]Cl. We present two experimental approaches using terahertz-infrared (THz-IR) pulses to probe the carrier distribution/conductivity: 1. Ultrafast photodoping, where the quasi-equilibrium is a hot electronic state with a non-thermal phonon distribution and significant deformation of the Hubbard bands (even for low excited carrier densities ∼1%). 2. Pressure-tuning across the MIT (below 30 MPa), where the THz dynamic conductivity senses metallic domains within the MI coexistence regime, complementary to DC transport where the MIT is dominated by a macroscopic percolation threshold.

Keywords: Mott-Hubbard; ultrafast; terahertz-infrared spectroscopy; photodoping; pressure-induced transition