Dresden 2020 – wissenschaftliches Programm
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CPP 93.7: Vortrag
Donnerstag, 19. März 2020, 12:00–12:15, WIL C107
Coupling broadband single-cycle THz pulses from a spintronic emitter to an STM junction — •Melanie Müller1, Natalia Martín Sabanés1,2, Sarojini Mahajan1, and Martin Wolf1 — 1Fritz Haber Institute, Berlin, Germany — 2Freie Universität Berlin, Berlin, Germany
THz-gated Scanning Tunneling Microscopy (THz-STM) combines sub-molecular spatial with femtosecond temporal resolution, as first impressively demonstrated in 2016 . Combined with plasmonic enhanced optical excitation THz-STM provides a powerful platform to study the atomically-resolved dynamics of photoexcited surfaces. We have developed an ultrahigh-vacuum STM for broadband excitation from the VIS through the THz spectral range. In particular, we employ an ultra-broadband (1-30 THz) spintronic THz emitter (STE) as source of single-cycle THz pulses to modulate the junction bias. To characterize the bandwidth, phase and voltage amplitude of the THz near-field, we sample the tip-enhanced THz waveform via THz-induced modulation of photocurrents . Careful comparison to the far-field waveform allows us to investigate the antenna properties of the STM tip. Considering strong tip-induced low pass filtering, frequencies up to 10 THz can be detected in the near-field. We further demonstrate versatile phase and polarity control of the THz waveform via the STE excitation conditions, and show that THz transients with a half-cycle period of 115 fs and several Volts amplitude can be achieved in the current setup. References:  Cocker T., el at, Nature 539, 263-267 (2016);  Yoshida S., et al, ACS Phot. 6, 1356-1364 (2019)