Macroscopic quantum phenomena such as high-temperature superconductivity, colossal magnetoresistance, ferrimagnetism and ferromagnetism arise from a delicate balance of different interactions among electrons, phonons and spins on the nanoscale1. The study of the interplay among these various degrees of freedom in strongly coupled electron–lattice systems is thus crucial to their understanding and for optimizing their properties. Charge-density-wave (CDW) materials2, with their inherent modulation of the electron density and associated periodic lattice distortion, represent ideal model systems for the study of such highly cooperative phenomena. With femtosecond time-resolved techniques, it is possible to observe these interactions directly by abruptly perturbing the electronic distribution while keeping track of energy relaxation pathways and coupling strengths among the different subsystems3,4,5,6,7. Numerous time-resolved experiments have been performed on CDWs8,9,10,11,12,13, probing the dynamics of the electronic subsystem. However, the dynamics of the periodic lattice distortion have been only indirectly inferred14. Here we provide direct atomic-level information on the structural dynamics by using femtosecond electron diffraction15 to study the quasi two-dimensional CDW system 1T-TaS2. Effectively, we have directly observed the atomic motions that result from the optically induced change in the electronic spatial distribution. The periodic lattice distortion, which has an amplitude of ∼0.1 Å, is suppressed by about 20% on a timescale (∼250 femtoseconds) comparable to half the period of the corresponding collective mode. These highly cooperative, electronically driven atomic motions are accompanied by a rapid electron–phonon energy transfer (∼350 femtoseconds) and are followed by fast recovery of the CDW (∼4 picoseconds). The degree of cooperativity in the observed structural dynamics is remarkable and illustrates the importance of obtaining atomic-level perspectives of the processes directing the physics of strongly correlated systems.
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Imada, M., Fujimori, A. & Tokura, Y. Metal-insulator transitions. Rev. Mod. Phys. 70, 1039–1263 (1998)
Grüner, G. Density Waves in Solids (Addison-Wesley, 1994)
Kusar, P. et al. Controlled vaporization of the superconducting condensate in cuprate superconductors by femtosecond photoexcitation. Phys. Rev. Lett. 101, 227001 (2008)
Ogasawara, T. et al. General features of photoinduced spin dynamics in ferromagnetic and ferrimagnetic compounds. Phys. Rev. Lett. 94, 087202 (2005)
Averitt, R. D. et al. Ultrafast conductivity dynamics in colossal magnetoresistance manganites. Phys. Rev. Lett. 87, 017401 (2001)
Rini, M. et al. Control of the electronic phase of a manganite by mode-selective vibrational excitation. Nature 449, 72–74 (2007)
Kübler, C. et al. Coherent structural dynamics and electronic correlations during an ultrafast insulator-to-metal phase transition in VO2 . Phys. Rev. Lett. 99, 116401 (2007)
Demsar, J., Biljakovic, K. & Mihailovic, D. Single particle and collective excitations in the one-dimensional charge density wave solid K0. 3MoO3 probed in real time by femtosecond spectroscopy. Phys. Rev. Lett. 83, 800–803 (1999)
Demsar, J. et al. Femtosecond snapshots of gap-forming charge-density-wave correlations in quasi-two-dimensional dichalcogenides 1T-TaS2 and 2H-TaSe2 . Phys. Rev. B 66, 041101 (2002)
Yusupov, R. V. et al. Single-particle and collective mode couplings associated with 1- and 2-directional electronic ordering in metallic RTe3 (R = Ho, Dy, Tb). Phys. Rev. Lett. 101, 246402 (2008)
Perfetti, L. et al. Time evolution of the electronic structure of 1T-TaS2 through the insulator-metal transition. Phys. Rev. Lett. 97, 067402 (2006)
Schmitt, F. et al. Transient electronic structure and melting of a charge density wave in TbTe3 . Science 321, 1649–1652 (2008)
Tomeljak, A. et al. Dynamics of photoinduced charge-density-wave to metal phase transition in K0. 3MoO3 . Phys. Rev. Lett. 102, 066404 (2009)
Schäfer, H. et al. Disentanglement of the electronic and lattice parts of the order parameter in a 1D charge density wave system probed by femtosecond spectroscopy. Phys. Rev. Lett. 105, 066402 (2010)
Miller, R. J. D. et al. ‘Making the molecular movie’: first frames. Acta Crystallogr. A 66, 137–156 (2010)
Williams, P. M., Parry, G. S. & Scruby, C. B. Diffraction evidence for Kohn anomaly in 1T-TaS2 . Phil. Mag. 29, 695–699 (1974)
Wilson, J. A. Di Salvo, F. J. & Mahajan, S. Charge-density waves and superlattices in the metallic layered transition-metal dichalcogenides. Adv. Phys. 24, 117–201 (1975)
Clerc, F. et al. Lattice-distortion-enhanced electron-phonon coupling and Fermi surface nesting in 1T-TaS2 . Phys. Rev. B 74, 155114 (2006)
Sipos, B. et al. From Mott state to superconductivity in 1T-TaS2 . Nature Mater. 7, 960–965 (2008)
Fazekas, P. & Tosatti, E. Electrical, structural and magnetic-properties of pure and doped 1T-TaS2 . Phil. Mag. B 39, 229–244 (1979)
Scruby, C. B., Williams, P. M. & Parry, G. S. The role of charge density waves in structural transformations of 1T-TaS2 . Phil. Mag. 31, 255–274 (1975)
Als-Nielsen, J. & McMorrow, D. Elements of Modern X-ray Physics Ch. 4.4.5 (Wiley, 2001)
Duffey, J. R., Kirby, R. D. & Coleman, R. V. Raman scattering from 1T-TaS2 . Solid State Commun. 20, 617–621 (1976)
Siwick, B. J., Dwyer, J. R., Jordan, R. E. & Miller, R. J. D. An atomic-level view of melting using femtosecond electron diffraction. Science 302, 1382–1385 (2003)
Chergui, M. & Zewail, A. H. Electron and X-ray methods of ultrafast structural dynamics: advances and applications. ChemPhysChem 10, 28–43 (2009)
Sciaini, G. et al. Electronic acceleration of atomic motions and disordering in bismuth. Nature 458, 56–59 (2009)
Sokolowski-Tinten, K. et al. Femtosecond X-ray measurement of coherent lattice vibrations near the Lindemann stability limit. Nature 422, 287–289 (2003)
Johnson, S. L. et al. Directly observing squeezed phonon states with femtosecond X-ray diffraction. Phys. Rev. Lett. 102, 175503 (2009)
Fritz, D. M. et al. Ultrafast bond softening in bismuth: mapping a solid’s interatomic potential with X-rays. Science 315, 633–636 (2007)
Beaud, P. et al. Ultrafast structural phase transition driven by photoinduced melting of charge and orbital order. Phys. Rev. Lett. 103, 155702 (2009)
We would like to acknowledge discussions with V. V. Kabanov, T. Dekorsy, D. Mihailovic, U. Bovensiepen and M. Wolf, and thank A. Nagy for help in preparing the video in Supplementary Material. This research was supported by the Sofja Kovalevskaja Award of the Alexander von Humboldt Foundation, the Center for Applied Photonics and Zukunftskolleg at the University of Konstanz, the Natural Science and Engineering Research Council of Canada and the Canada Foundation for Innovation. M.E. acknowledges financial support through the Stiftung der Deutschen Wirtschaft. H.B. acknowledges financial support from the Swiss NSF and the NCCR MaNEP.
The authors declare no competing financial interests.
This file contains Supplementary Information comprising Experimental Details and Detailed Data Analysis, Supplementary Figures 1-6 with legends, Legends for Supplementary Movies 1-3 and additional references. (PDF 2126 kb)
This movie shows the time evolution of the differential diffraction from -1 to 6 ps with 100 fs time steps, recorded at the excitation density F = 2.4 mJ/cm2. (AVI 2122 kb)
This movie shows the animation of the emerging time-evolution of the real-space structure, including both lattice dynamics and the dynamics of the conduction electron density. (AVI 10360 kb)
This movie shows the animation of the corresponding changes in the momentum space. (AVI 10175 kb)
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Eichberger, M., Schäfer, H., Krumova, M. et al. Snapshots of cooperative atomic motions in the optical suppression of charge density waves. Nature 468, 799–802 (2010). https://doi.org/10.1038/nature09539
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