Atomic-Scale Terahertz Near Fields for Ultrafast Tunnelling Spectroscopy

Lightwave-driven terahertz scanning tunnelling microscopy (THz-STM) is capable of exploring ultrafast dynamics across a wide range of materials with angstrom resolution. In contrast to scanning near-field optical microscopy, where photons scattered by the tip apex are analyzed to access the local di...

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Bibliographic Details
Published in:arXiv.org 2023-10
Main Authors: Jelic, Vedran, Adams, Stefanie, Hassan, Mohamed, Cleland-Host, Kaedon, Ammerman, S Eve, Cocker, Tyler L
Format: Article
Language:English
Subjects:
Dielectric strength
Electron states
Microscopy
Near fields
Optical microscopy
Scanning tunneling microscopy
Spectral resolution
Spectroscopy
Spectrum analysis
Tunnel junctions
Waveforms
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Summary:Lightwave-driven terahertz scanning tunnelling microscopy (THz-STM) is capable of exploring ultrafast dynamics across a wide range of materials with angstrom resolution. In contrast to scanning near-field optical microscopy, where photons scattered by the tip apex are analyzed to access the local dielectric function on the nanoscale, THz-STM uses a strong-field single-cycle terahertz pulse to drive an ultrafast current across a tunnel junction, thereby probing the local density of electronic states. Yet, the terahertz field in a THz-STM junction may also be spectrally modified by the electromagnetic response of the sample. Here, we demonstrate a reliable and self-consistent approach for terahertz near-field waveform acquisition in an atomic tunnel junction that can be generally applied to electrically conductive surfaces. By combining waveform sampling and tailoring with terahertz scanning tunnelling spectroscopy (THz-STS), we comprehensively characterize the tunnel junction and distinguish local sample properties from effects due to terahertz pulse coupling and field enhancement. Through modelling, we verify the presence of an isolated unipolar terahertz-induced current pulse, facilitating straightforward interpretation for differential THz-STS with high spectral resolution. Finally, we demonstrate the feasibility of atomic-scale terahertz time-domain spectroscopy via the extremely localized near-fields in the tunnel junction.
ISSN:2331-8422
DOI:10.48550/arxiv.2310.14335