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Femtosecond electron diffraction: Heralding the era of atomically-resolved dynamics Germán Sciaini Max Planck Research Department for Structural Dynamics, Center for Free Electron Laser Science, DESY & Physics Department, University of Hamburg 1

Femtosecond electron diffraction (FED) layout Ultrafast Structural Dynamics For recent advances in the field, see: G. Sciaini and R.J.D. Miller. Rep. Prog. Phys. 74, 096101 (2011). FED – similar effective brightness to 4 th generation fs X-ray sources LCLS 200-keV FED setup European XFEL 2

FED fs X-ray SLS — 3 rd generation LS, slicing DC compact e-guns 200-300 fs 200 fs 10 8 -10 9 ph/pulse 300 ph/pulse New DC e-gun designs Plasma sources 100-300 fs 100 fs 10 9 -10 10 ph/pulse. 10 3 ph/pulse. 4 th generation light sources. RF-compression e-guns ~ sub-100 fs (250 fs) sub-100 fs (100 fs) 10 10 -10 11 ph/pulse 10 12 ph/pulse Relativistic e-guns ~ sub-100 fs (200 fs) 10 10 -10 12 ph/pulse For recent advances in FED see: G. Sciaini & R.J.D. Miller . Rep. Prog. Phys. 74 096101 (2011). 3

Ponderomotive force: Ponde Major advance over conventional streak camera technologies. 4 Hebeisen, Sciaini et al. Opt Express 16, 3334 (2008)

Single shot versus reversible FED experiments 5

FED experiments under nonreversible conditions “single shot” Sample is moved between shots 6

Over a century of theories to explain “Melting” Heterogeneous-- Surface 20 ps 500 ps 100 ps Homogeneous--Bulk 3 ps 4 ps 5 ps Sutherland W. Philos. Magazine (1891) 32:194, 31-43. Lin et al. J. Phys. Chem. C 114, 5686 (2010) 7

G. Sciaini et al., Nature 458, 56 (2009). Optical phonon period! In news & views, Nature 458 , 42 (2009). 8

A. Cavalleri. Nature (news & views) 458 , 42 (2009) Sciaini et al . irradiate crystalline bismuth with ultrashort bursts of electrons to monitor the emergence of atomic disorder during laser-induced melting. The images show electron-diffraction patterns observed before (a) and after (b) laser excitation. Atomic disorder emerges in about 200 femtoseconds (0.2 picoseconds). (Modified from a graphic by J. Harms.) 9

FED experiments under reversible conditions 10

D T = 320K Unit cell changes ~ 10 -3 Å Shear mode detection becomes trivial detectable. Full Characterization of Mechanical Properties of Nanomaterials 11 Harb et al. Phys. Rev. B 79, 094301 (2009)

STM image – real space Reciprocal space Θ ~ 10 o http://www.physnet.uni-hamburg.de/iap/group_g/F_Praktikum/Rastertunnelmikroskopie/ 12

Fluence: 2.4 mJ/cm 2 D T(pump) ~ 90 K 13 CDW_movie

Movie_recip Movie_real Initial amplitude of the periodic lattice distortion ~ 0.1 Å. Atomic displacements ~ 0.02 Å 14

Submitted to Nature. 15

Insulator-to-Metal phase transition in (EDO-TTF) 2 PF 6. (TMTSF) 2 PF 6 First organic superconductor Chollet et al., Science 307, 86 (2005). (EDO-TTF) 2 PF 6 100-nm thick samples 100-keV FED setup In collaboration with: Prof. Shin-ya Koshihara Prof. Ken Onda Tokyo Institute of Technology Prof. Hideki Yamochi Kyoto University 16 M. Gao, et al., submitted to Nature.

Organic samples: a challenging problem Sample degradation – diffracted intensity vs. # 100 nm thick samples, images – polarized light microscope of laser shots; @ (a) 1 kHz; (b) 10 Hz. (b) (a) Masked dynamics due to accumulative heating @ 1 kHz Gao M, Jean-Ruel J et al., Opt. Express 20, 12048 (2012). 10 Hz 200000 e/pulse 280 um spot size IRF – 0.4 ps (FWHM) M. Gao, et al., submitted to Nature 17

Time-resolved studies implementing a recently developed Ultrabright FED setup @ 10 Hz Time-dependent photo-induced Thermal phase transition differential intensity changes Over 200 reflections showing time-resolved Intensity changes beyond SNR. M. Gao, et al., submitted to Nature.

Unpublished results Coming soon… 19

Acknowledgments Toronto/Hamburg Prof. R.J.Dwayne Miller Universität Duisburg-Essen Wisconsin Madison Present members/Toronto Prof. Michael Horn-von Hoegen Prof. Max Lagally Dr. Gustavo Moriena Dr. Frank Meyer zu Heringdorf Prof. Mark Eriksson Hubert Jean-Ruel Thomas Payer Weina Peng Ray Gao Lai Chung Liu Past members Tokyo Institute of Technology U of Konstanz Prof. Ralph Ernstorfer Prof. Shin-ya Koshihara Prof. Jure Demsar Dr. Maher Harb Prof. Ken Onda Maximilian Eichberger Dr. Thibault Dartigalongue Hanjo Shäfer Dr. Christoph Hebeisen Kyoto University Dr. Sergei Kruglik Prof. Hideki Yamochi EPFL Dr. Cheng Lu & co-workers. Dr. Helmuth Berger Dr. Ryan Cooney Canadian Light Source Dr. Mark de Jong Dr. Jonathan Stampe 20

Thank you! Thank you for your attention!