Regensburg 2022 – scientific programme
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MA: Fachverband Magnetismus
MA 21: Terahertz Spintronics
MA 21.1: Talk
Wednesday, September 7, 2022, 09:30–09:45, H43
Spintronic THz emitters for lightwave-driven scanning tunneling microscopy at MHz repetition rates — •Alkisti Vaitsi1, Vivien Sleziona1, Fabian Schulz2, Luis Enrique Parra Lopez1, Tom Sebastian Seifert1,3, Martin Wolf1, and Melanie Müller1 — 1Fritz Haber Institute of the Max Planck Society, Berlin, Germany — 2CIC NanoGUNE BRTA, San Sebastian, Spain — 3Freie Universität Berlin, Germany
Attaining simultaneous high temporal resolution and signal-to-noise ratio in THz lightwave-driven scanning tunneling microscopy (THz-STM) requires broadband single-cycle THz pulses at high repetition rates and electric field strength. In this context, we report on the operation of ultrabroadband spintronic THz emitters (STE) at MHz repetition rates and pump powers of several Watts. We discuss saturation mechanisms which can reduce THz emission efficiency, such as steady-state and transient heating, limiting the usable fluence at the STE. Furthermore, to maximize the THz field in the STM junction, we analyze and optimize THz propagation into the STM, which due to the ultrabroadband spectrum of the STE requires careful consideration of pump spot sizes in combination with the limitations arising from pump fluence and average pump power density. We present detailed experimental and theoretical analysis of the ideal excitation geometry, which allows STE operation up to 10 W average powers at 2 MHz repetition rate at optimized fluence and THz propagation into the STM.