Time resolution of terahertz scanning tunneling microscopy measurements inside a superconducting magnet using a hollow waveguide

A terahertz scanning tunneling microscope (THz-STM) is an STM that allows us to perform time-resolved measurements of tunneling currents with high temporal resolution, in addition to the high spatial resolution of STMs. In such a device, it is necessary to guide the THz beam to the STM tip, which can be difficult if there are tight space restrictions due to experimental requirements, such as ultra-high vacuum and high magnetic fields. We aim to develop a THz-STM that allows us to measure tunneling currents in high magnetic fields at cryogenic temperatures with a time resolution on the order of picoseconds. In this paper, we placed a specially designed chamber containing a homemade STM head inside a superconducting magnet and performed time-resolved measurements of the tunneling current between the Pt-Ir tip and a highly oriented pyrolytic graphite (HOPG) sample. To introduce the THz pulse into the STM chamber, we used a narrow pipe as a waveguide and evaluated a time resolution of better than 1 ps, which suggests that the realization of a THz-STM for multi-extreme conditions with picosecond time resolution is possible.