Variable-temperature lightwave-driven scanning tunneling microscope with a compact, turn-key terahertz source.

ABSTRACT

We report on a lightwave-driven scanning tunneling microscope based on a home-built microscope and a compact, commercial, and cost-effective terahertz-generation unit with a repetition rate of 100 MHz. The measurements are performed in an ultrahigh vacuum at temperatures between 8.5 and 300 K. The cross-correlation of the pump and probe pulses indicates a temporal resolution on the order of a picosecond. In terms of spatial resolution, CO molecules, step edges, and atomically resolved terraces are readily observed in terahertz images, with sometimes better contrast than in the topographic and (DC) current channels. The utilization of a compact, turn-key terahertz-generation system requires only limited experience with optics and terahertz generation, which may facilitate the deployment of the technique to further research groups.