Dresden 2026 – scientific programme

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O: Fachverband Oberflächenphysik

O 43: Scanning probe microscopy: light matter interaction at atomic scales – Poster

O 43.4: Poster

Tuesday, March 10, 2026, 14:00–16:00, P2

Focal phase evolution of single-cycle THz near-field pulses in a scanning tunneling microscope — •Andrea Rossetti, Vivien Sleziona, Alkisti Vaitsi, Luis Enrique Parra Lopez, Martin Wolf, and Melanie Müller — 1Department of Physical Chemistry, Fritz Haber Institute, 14195 Berlin, Germany

Lightwave scanning tunneling microscopy (LW-STM) employs single-cycle THz pulses as femtosecond bias, enabling imaging at sub-nanometer spatial and sub-picosecond temporal resolution. Control over the polarity and carrier-envelope phase (CEP) of such THz voltage transients is thereby crucial in determining which electronic states contribute to the ultrafast tunneling current. A simple approach for continuous CEP control of the single-cycle THz transients in LW-STM is via the Gouy phase. In this work, using a spintronic THz emitter, we use photoemission sampling from the point-like apex of the STM tip to monitor the local CEP of the tip-enhanced THz pulses along the focal axis of a focused THz beam. We find that the CEP exhibits a non-trivial evolution through the focus that strongly deviates from the expected Gouy phase shift for a monochromatic beam. Using analytical models and numerical calculations, we discuss the influence of the broad bandwidth of the THz pulses as well as their coupling to the STM tip for the local CEP in LW-STM.

Keywords: THz-STM; Gouy phase; strong-field light-matter interaction; carrier-envelope phase; tip-enhanced THz pulses