Monday, April 25, 2016 - 16:00
Event Speaker: 
Robert Kaindl (Lawrence Berkeley National Laboratory)
Local Contact: 
Yun-Shik Lee

Ultrafast and nanoscale phenomena in complex materials are closely linked, motivating experiments that access these extremes to clarify the fundamental physics.  In this talk, I will discuss the application of ultrashort light pulses – from THz to X-rays – to the study of dynamics, interactions, and emergent correlations in complex materials.  In particular, transition-metal oxides exhibit an intriguing self-organization of charges into nanoscale “stripes”, whose dynamic driving forces and role in high‑TC superconductivity remain unresolved.  I will present recent mid-IR and THz experiments that track the initial steps of charge ordering in stripe-phase nickelates, indicating the role of charge localization and transient electron-phonon coupling as precursors of stripe formation. Moreover, transient multi-THz spectroscopy allows us to capture the dynamics of vibrational symmetry breaking, exposing the electronic and structural coupling during stripe melting and formation.  Finally, I will briefly discuss the development of a new capability for ultrafast photoemission spectroscopy with extreme-ultraviolet pulses at high repetition rates, which can provide a complementary momentum-space view of electronic dynamics and correlations. The experiments yield new insight into the physics of quantum materials, motivating further ultrafast studies to probe and ultimately control solids on fundamental length, energy and time scales.