Berlin 2024 – scientific programme
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O: Fachverband Oberflächenphysik
O 54: Scanning Probe Microscopy: Light Matter Interaction at Atomic Scales I
O 54.7: Talk
Wednesday, March 20, 2024, 17:00–17:15, MA 041
Observing correlated electron dynamics in the local density of states of 1T-TaS2 by THz-STM — •Luis Parra López1, Alkisti Vaitsi1, Vivien Sleziona1, Fabian Schulz2, Martin Wolf1, and Melanie Müller1 — 1Fritz Haber Institute, Berlin, Germany — 2CIC nanoGUNE, San Sebastian, Spain
THz scanning tunneling microscopy (THz-STM) has emerged as a promising technique for imaging surfaces with femtosecond temporal and angstrom spatial resolution. The prospect of imaging both local charge and lattice dynamics is of particular interest for the study of strongly correlated materials whose physical properties are governed by strong electron-electron and electron-phonon interactions. 1T-TaS2 is a fascinating example, where the formation of a commensurate charge density wave (C-CDW) phase is accompanied by the opening of a Mott gap. Femtosecond optical excitation leads to ultrafast collapse of the Mott gap and launches coherent amplitude motion of the CDW. We discuss to what extent both can be probed by THz-STM and decipher the mechanisms by which transient electronic temperatures, ultrafast Mott collapse and coherent AM oscillations modulate the tunneling current. We present a model to extract ultrafast changes in the local density of states in the C-CDW phase of 1T-TaS2. We reproduce the transient change of the rectified current measured in THz-STM after global ultrafast photoexcitation of 1T-TaS2. Our results provide the basis to explore ultrafast insulator-to-metal transitions and coherent CDW oscillations with the angstrom spatial resolution provided by THz-STM.
Keywords: Strongly correlated materials; THz-STM; TMDs; Coherent phonons