Structure and Dynamics with Ultrafast Electron Microscopes

… or how to make atomic-level movies of molecules and materials 

In this talk I will describe how combining ultrafast lasers and electron microscopes in novel ways makes it possible to directly ‘watch’ the time-evolving structure of condensed matter on the fastest timescales open to atomic motion.  By combining such measurements with complementary (and more conventional) spectroscopic probes one can develop structure-property relationships for materials under even very far from equilibrium conditions.

I will give several examples of the remarkable new kinds of information that can be gleaned from such studies and describe how these opportunities emerge from the unique capabilities of the current generation of ultrafast electron microscopy instruments.  For example, in diffraction mode it is possible to identify and separate lattice structural changes from valence charge density redistribution in materials on the ultrafast timescale and to identify novel photoinduced phases that have no equilibrium analogs.   It is also possible to directly probe the strength of the coupling between electrons and phonons in materials across the entire Brillouin zone and to probe nonequilibrium phonon dynamics (or relaxation) in exquisite detail.  In imaging mode, real space pictures of nano- to microstructural evolution in materials at unprecedented spatio-temporal resolution can be obtained. 

I will assume no familiarity with ultrafast lasers or electron microscopes.

References

1. G. Sciani and  R. J. D. Miller, Femtosecond electron diffraction:  Heralding the era of atomically resolved dynamics, Rep. Prog. Phys. 71 (2011) 096101
2. R. P. Chatelain, V. Morrison, C. Godbout, and B.  J. Siwick, Ultrafast electron diffraction with radio-frequency compressed electron pulses, Appl. Phys. Lett. 101 (2012) 081901.
3. V. Morrison, R. P. Chatelain, K. Tiwari, A. Hendaoui, M. Chakker and B.  J.  Siwick, A photoinduced metal-like phase of monoclinic vanadium dioxide revealed by ultrafast electron diffraction, Science 346 (2014) 445 – 448.
4. R. P. Chatelain, V. Morrison, Bart L. M. Klarenaar and B.  J.  Siwick, Coherent and incoherent electron-phonon coupling in graphite observed with radio-frequency compressed ultrafast electron diffraction, Phys. Rev. Lett. 113 (2014) 235502.
5. L. Nikolova, M. Stern, T. LaGrange, B. Reed, N. Browning, G. H. Campbell, J.-C. Kieffer, F. Rosei and B. J. Siwick, Complex crystallization dynamics in amorphous germanium studied with dynamic TEM. Phys. Rev. B 87 (2013) 064105.