Sub-cycle nanooptics in the strong-field limit

• Applicant: Professor Dr. Rupert Huber, since 1/2018
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277164313

• Final Report Year: 2020

Final Report Abstract

This project combined high-power, phase-locked THz transients with scanning probe microscopy to explore high-sensitivity linear, nonlinear, and strong-field light-matter interaction on ultrashort length and time scales. We pursued several approaches to reach this goal. First, we developed and set up a roomp temperature scanning near-field optical microscopy (SNOM) system based on a femtosecond thin-disk high-power laser oscillator, a custom-tailored pulse compression scheme, and an optical rectification stage generating phase-locked multi-THz pulses with an average power of up to 80 mW. Whereas the strongest THz near fields led to undesired changes to the apex of the scanning tip, we found that important ultrafast pump-probe spectroscopy could still be performed with high sensitivity if the field strength is kept below the tip damage threshold. In this regime, we studied the insulator-metal phase transition in VO2, switchable plasmons on black phosphorus, surface states on topological insulators, and charge transport on transition metal dichalcogenide heterostructures. In parallel, we found that stable operation of scanning tips may be achieved even under atomically strong THz fields if we isolate them from the ambient environment. In close collaboration with the group of Prof. Jascha Repp at the University of Regensburg, we developed the first-ever low-temperature THz-driven scanning tunneling microscope (STM). This allowed us to resolve the ultrafast dynamics of a single molecule on the Ångström length scale and sub-cycle time scale. The atomically precise strong-field light-matter interaction underlying these experiments opened an entirely new parameter space, which has been well received by the media and the international scientific community and enticed numerous research groups worldwide to embark on this exciting new research topic.

Publications

• Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging. Nature 539, 263-267 (2016)
  T. L. Cocker, D. Peller, P. Yu, J. Repp and R. Huber
  
• Ultrafast mid-infrared nanoscopy of strained vanadium dioxide nanobeams. Nano Letters 16, 1421-1427 (2016)
  M. A. Huber, M. PlankI, M. Eisele, R. E. Marvel, F. Sandner, T. Korn, C. Schüller, R. F. Haglund, R. Huber, and T. L Cocker
  
• Femtosecond photo-switching of interface polaritons in black phosphorus heterostructures. Nature Nanotechnology 12, 207-211 (2017)
  M. A. Huber, F. Mooshammer, M. PlankI, L Viti, F. Sandner, L. Z. Kastner, T. Frank, J. Fabian, M. S. Vitiello, T. L. Cocker and R. Huber
  
• Nanoscale near-field tomography of surface states on (Bi0.5Sb0.5)2Te3. Nano Letters 18, 7515-7523 (2018)
  F. Mooshammer, F. Sandner, M. A. Huber, M. Zizisperger, H. Weigand, M. PlankI, C. Weyrich, M. Lanius, J. Kampmeier, G. Mussler, D. Grützmacher, J. L. Boland, T. L. Cocker, and R. Huber