Atto- und Femtosekundenkontrolle von kohärenten Elektronen in Tieftemperaturnanomaterialien und niederdimensionalen Nanomaterialien

• Antragsteller: Professor Dr. Matthias Kling, seit 4/2020
• Fachliche Zuordnung: Experimentelle Physik der kondensierten Materie ; Optik, Quantenoptik und Physik der Atome, Moleküle und Plasmen
• Förderung: Förderung von 2018 bis 2022
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 389759512

• Erstellungsjahr: 2022

Zusammenfassung der Projektergebnisse

By irradiating a nanoscale object with femtosecond laser pulses, optical fields are localized at geometrical inhomogeneities such as sharp corners of the object. The localized optical fields then induce ultrafast electron emission from them. The ultrafast emission can be used to create ultrafast devices that are three to six orders of magnitude faster than current devices. The localized field distribution can be controlled with their optical parameters and thus realized spatial controllability of electron source on a scale of about 10 nm. Because the coherence length of metal is about 10 nm, the resolution of an optically-controlled electron source just enters a quantum regime. However, further miniaturization of such a spatially controllable electron source down to an atomistic scale smaller than 1 nm, where electronic systems are quantized, is technically difficult via plasmonics, and a paradigm shift is required. In this project, we realized that paradigm shift by employing a single-molecule electron source that we identified. By applying strong fields to molecules deposited on a metallic surface, we found that most of the molecules were evaporated and single-molecule protrusions appeared on a molecular layer. The single-molecule protrusions then become electron sources and generate peculiar electron emission patterns such as clover leaves. These patterns were first observed seventy years ago. However, the formation mechanism of the patterns has been debated since then. Here, we introduce a simulation model using quantum theory. The simulations revealed that the patterns represent the spatial distributions of electrons in a single molecule or its molecular orbitals (MOs) around the Fermi level of the metal substrate. Because spatial distributions of MOs vary with their energy, we envisioned that an optically-modulated electron source would be created by selecting other MOs by light. The idea was indeed realized by illuminating femtosecond light pulses. We successfully visualized MOs at an excited energy level and largely modulated emission patterns. Thus, we have achieved optical modulation of electron source on a scale of sub-1 nm using quantum effects.

Projektbezogene Publikationen (Auswahl)

• Laser-induced field emission from a tungsten nanotip by circularly polarized femtosecond laser pulses, Phys. Rev. B, 101, 045406 (2020)
  H. Yanagisawa, T. Greber, C. Hafner, and J. Osterwalder
  
• Femtosecond Laser Induced Resonant Tunneling in an indivisual Quantum Dot Attached to a Nanotip, ACS Photonics 8, 505 (2021)
  M. Duchet, S. Perisanu, S. T. Purcell, E. Sonstant, V. Loriot, H. Yanagisawa, M. F. Kling, F. Lepine, and A. Ayari
  
• Onset of charge interaction in strongfield photoemission from nanometric needle tips, Nanophotonics 10, 3769-3775 (2021)
  J. Schötz, L. Seiffert, A. Maliakkal, J. Blöchl, D. Zimin, P. Rosenberger, B. Bergues, P. Hommelhoff, F. Krausz, T. Fennel, M.F. Kling
  
• Field emission microscope for a single fullerene molecule, Scientific Reports 12, 2174 (2022)
  H. Yanagisawa, M. Bohn, F. Goschin, A.P. Seitsonen and M.F. Kling
  
• Subnanometeric optical modulation of a single-molecule electron source
  H. Yanagisawa, M. Bohn, H. Kitoh, F. Goschin and M.F. Kling