title: Delayed electron emission in strong-field driven tunnelling from a metallic nanotip in the multi-electron regime.
abstract: Illuminating a nano-sized metallic tip with ultrashort laser pulses leads to the emission of electrons due to multiphoton excitations. As optical fields become stronger, tunnelling emission directly from the Fermi level becomes prevalent. This can generate coherent electron waves in vacuum leading to a variety of attosecond phenomena. Working at high emission currents where multi-electron effects are significant, we were able to characterize the transition from one regime to the other. Specifically, we found that the onset of laser-driven tunnelling emission is heralded by the appearance of a peculiar delayed emission channel. In this channel, the electrons emitted via laser-driven tunnelling emission are driven back into the metal, and some of the electrons reappear in the vacuum with some delay time after undergoing inelastic scattering and cascading processes inside the metal. Our understanding of these processes gives insights on attosecond tunnelling emission from solids and should prove useful in designing new types of pulsed electron sources.
authors: Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland.|Physik-Institut, Universität Zürich, CH-8057 Zürich, Switzerland.|Max Planck Institute of Quantum Optics, D-85748 Garching, Germany.|Max Planck POSTECH/KOREA Res. Init., Pohang, 37673, South Korea.|Physics Department, Ludwig-Maximilians-Universität München, D-85748 Garching, Germany.
authors: Hirofumi
authors: H
authors: Yanagisawa
authors: Laboratory for Electromagnetic Fields and Microwave Electronics, CH-8092 Zürich, Switzerland.
authors: Sascha
authors: S
authors: Schnepp
authors: Laboratory for Electromagnetic Fields and Microwave Electronics, CH-8092 Zürich, Switzerland.
authors: Christian
authors: C
authors: Hafner
authors: Physik-Institut, Universität Zürich, CH-8057 Zürich, Switzerland.
authors: Matthias
authors: M
authors: Hengsberger
authors: Max Planck POSTECH/KOREA Res. Init., Pohang, 37673, South Korea.|Department of Physics, POSTECH, Pohang, 37673, South Korea.
authors: Dong Eon
authors: DE
authors: Kim
authors: Max Planck Institute of Quantum Optics, D-85748 Garching, Germany.|Physics Department, Ludwig-Maximilians-Universität München, D-85748 Garching, Germany.
authors: Matthias F
authors: MF
authors: Kling
authors: Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland.|Max Planck POSTECH/KOREA Res. Init., Pohang, 37673, South Korea.|Department of Physics, POSTECH, Pohang, 37673, South Korea.
authors: Alexandra
authors: A
authors: Landsman
authors: Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland.|Institute of Applied Physics, University of Bern, CH-3012 Bern, Switzerland.
authors: Lukas
authors: L
authors: Gallmann
authors: Physik-Institut, Universität Zürich, CH-8057 Zürich, Switzerland.
authors: Jürg
authors: J
authors: Osterwalder