Phase-Resolved Detection of Ultrabroadband THz Pulses inside a Scanning Tunneling Microscope Junction
| Autor: | Melanie Müller, Martin Wolf, Natalia Martín Sabanés, Tobias Kampfrath |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
THz voltage sampling
Materials science Terahertz radiation FOS: Physical sciences Applied Physics (physics.app-ph) 02 engineering and technology 01 natural sciences Article law.invention 010309 optics law Mesoscale and Nanoscale Physics (cond-mat.mes-hall) 0103 physical sciences Waveform Electrical and Electronic Engineering Common emitter Condensed Matter - Mesoscale and Nanoscale Physics Spintronics business.industry spintronic THz emitter Physics - Applied Physics 021001 nanoscience & nanotechnology Atomic and Molecular Physics and Optics broadband THz pulses 3. Good health Electronic Optical and Magnetic Materials ultrafast photocurrents Femtosecond scanning tunneling microscopy Optoelectronics Scanning tunneling microscope 0210 nano-technology business Ultrashort pulse tip antenna response Biotechnology Voltage |
| Zdroj: | ACS Photonics |
| ISSN: | 2330-4022 |
| DOI: | 10.1021/acsphotonics.0c00386 |
| Popis: | Coupling phase-stable single-cycle terahertz (THz) pulses to scanning tunneling microscope (STM) junctions enables spatio-temporal imaging with femtosecond temporal and \r{A}ngstrom spatial resolution. The time resolution achieved in such THz-gated STM is ultimately limited by the sub-cycle temporal variation of the tip-enhanced THz field acting as an ultrafast voltage pulse, and hence by the ability to feed high-frequency, broadband THz pulses into the junction. Here, we report on the coupling of ultrabroadband (1-30 THz) single-cycle THz pulses from a spintronic THz emitter(STE) into a metallic STM junction. We demonstrate broadband phase-resolved detection of the THz voltage transient directly in the STM junction via THz-field-induced modulation of ultrafast photocurrents. Comparison to the unperturbed far-field THz waveform reveals the antenna response of the STM tip. Despite tip-induced low-pass filtering, frequencies up to 15 THz can be detected in the tip-enhanced near-field, resulting in THz transients with a half-cycle period of 115 fs. We further demonstrate simple polarity control of the THz bias via the STE magnetization, and show that up to 2 V THz bias at 1 MHz repetition rate can be achieved in the current setup. Finally, we find a nearly constant THz voltage and waveform over a wide range of tip-sample distances, which by comparison to numerical simulations confirms the quasi-static nature of the THz pulses. Our results demonstrate the suitability of spintronic THz emitters for ultrafast THz-STM with unprecedented bandwidth of the THz bias, and provide insight into the femtosecond response of defined nanoscale junctions. Comment: 5 figures, supporting information available |
| Databáze: | OpenAIRE |
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