Event Date Details:
Refreshments served at 3:40 p.m.
- Broida 1640
- Physics Colloquium
Periods of condensed matter research have often been defined by the exploration of new frontiers at experimental extremes. Innovative tools developed to redraw these boundaries have allowed scientists to make exciting advances, such as revealing exotic phenomena at low temperatures, controlling quantum behavior in nanosystems, or discovering transient nonequilibrium states on ultrafast time scales. Recently, a new experimental frontier has emerged with the potential to significantly impact physics, chemistry, materials science, and biology: the regime of ultrafast and ultrasmall. This is the domain in which single atoms, molecules, and electronic orbitals move, oscillating and changing with characteristic periods of femtoseconds to picoseconds. The ultimate goal of experimentalists studying these dynamics – regardless of their technique – has thus been to resolve such intrinsic motion with simultaneous atomic spatial resolution and temporal resolution faster than a single oscillation cycle. In this talk, I will show how this goal can be achieved using new techniques based on combining terahertz technology with scanning probe microscopy. I will tour the audience through the development of this approach, starting with ultrafast terahertz spectroscopy of nanoparticle ensembles, progressing to near-field microscopy of single nanoparticles with femtosecond temporal resolution, and culminating with lightwave terahertz scanning tunneling microscopy, where the oscillating electric field of a phase-stable, few-cycle light pulse is used to remove a single electron from a single molecular orbital within a time window faster than an oscillation cycle of the terahertz wave. Finally, I will show how this technique has been used to take ultrafast snapshot images of single molecular orbitals and watch the motion of a single molecule for the first time.