Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 23: Poster Ultrafast Electron Dynamics
O 23.1: Poster
Montag, 17. März 2025, 18:00–20:00, P2
Charge Density Waves and Doublon Lifetime in Doped 1T-TaS2 — •J. Jayabalan1, Gaël Reecht1, Florian Diekmann2, Ping Zhou1, Walter Schnelle3, Kai Roßnagel2, Manuel Gruber1, and Uwe Bovensiepen1 — 1Universität Duisburg-Essen, Germany. — 2Christian-Albrechts-Universität zu Kiel, Germany. — 3Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
Below a certain critical temperature, the periodic rearrangement of atoms into a long-range ordered star-like pattern transforms the metallic 1T-TaS2 into an insulating state by opening a band gap [B. Sipos, et al., Nature Materials 7, 960 (2008)]. This metal-to-insulator transition progresses through distinct charge density wave (CDW) states, driven by the interplay between electron-electron and electron-lattice interactions. In the commensurate CDW state of 1T-TaS2, the carriers excited into its upper Hubbard band (UHB), also known as a doublon state, decay in less than 20 fs due to the presence of unintentionally doped holes in the sample [M. Ligges, et al., Phys. Rev. Lett., 120, 166401 (2018)]. Through ultraviolet time-resolved photoemission spectroscopy at the Γ point, we identify a long-lived feature near the upper Hubbard band (UHB) energy in 1T-Ta(1−x)WxS2. Through variations in temperature, doping concentration, and pump-induced effects, we identify this observed feature as long-lived doublons. With STM measurements, we show a long living hole dynamics through localized excitations at specific locations of the sample. Funding by the DFG through FOR 5249 QUAST is gratefully acknowledged.
Keywords: Strongly correlated systems; Charge density waves; Doublons; Electron-Electron interactions; Electron-Phonon interactions