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

This article focuses on the development and evaluation of a terahertz scanning tunneling microscope (THz-STM) designed to perform time-resolved tunneling current measurements under multi-extreme conditions, including high magnetic fields (up to 10 T) and cryogenic temperatures. The authors implemented a homemade PAN-type STM head inside a superconducting magnet and introduced THz pulses to the STM tip via a narrow stainless-steel pipe acting as a waveguide, achieving a time resolution better than 1 picosecond for the main tunneling current peak and about 10 picoseconds when including sidelobe effects. Experimental results using a Pt–Ir tip and highly oriented pyrolytic graphite (HOPG) sample demonstrated that the THz pulse functions as an instantaneous bias, enabling picosecond-scale time-resolved measurements despite beam attenuation and waveform distortion through the waveguide. These findings suggest the feasibility of THz-STM operation with high temporal resolution in environments combining ultra-high vacuum, strong magnetic fields, and low temperatures, expanding the technique's applicability for nanoscale electronic spectroscopy and imaging.