In a Born-Oppenheimer description, atomic motions evolve across a potential energy surface determined by the occupation of electronic states as a function of atom positions. Ultrafast photo-induced phase transitions provide a test case for how the forces and resulting nuclear motion along the reaction co-ordinate originate from a non-equilibrium population of excited electronic states. Here I discuss recent advances in time-resolved photoemission spectroscopy allowing for direct probing of the underlying fundamental steps and the transiently evolving band structure in the ultrafast phase transition in indium nanowires on Si(111) . Furthermore, I will discuss some recent attempts to access the space-time limit in surface dynamics using local optical excitation of controlled plasmonic nano-junctions and tip-enhanced Raman scattering (TERS) [2,3].
 C.W. Nicholson et al., Science 362, 821 (2018) & PRB 99, 155107 (2019).
 S. Liu et al. PRL 121, 226802 (2018) & Nano Lett. 19, 5725(2019).
 H. Böckmann et al., J. Phys. Chem. Lett. 10, 2068 (2019).
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