Ultrafast physics in scanning tunneling microscopy and Dirac materials

Attosecond science enables the real-time study of ultrafast electron dynamics in matter through control of the sub-cycle waveform of strong laser pulses. In our lab, we investigate signatures of many-body electron dynamics of condensed matter systems, nanostructures and molecules on ultrafast time scales. In a first study, we integrate a conventional scanning tunneling microscope (STM) with an ultrafast femtosecond laser. We demonstrate attosecond control of the electric current in the nanoscale STM tunneling junction using the waveform of the laser field. We also introduce a strong-field model which explains the physics of ultrafast STM currents in all interaction regimes. Ultrafast STM promises simultaneous ångström and attosecond observations of plasmonic dynamics and ultrafast many-body phenomena in organic molecules.

The second part of my talk focuses on the hallmark effect of attosecond science, high-harmonic generation (HHG), carried out in graphene. Compared to conventional materials, we observe strong saturation of the carrier excitation in the Dirac material due to the vanishing band gap. We also measure the quantum properties of harmonic light and find that the saturation leads to nonclassical squeezed light. Dirac materials may open up a new route to obtain quantum light in the ultraviolet regime at the interface of attosecond science and quantum optics.