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Advances in Condensed Matter Physics
Volume 2010 (2010), Article ID 958618, 27 pages
doi:10.1155/2010/958618
Review Article

Real-Time Observation of Cuprates Structural Dynamics by Ultrafast Electron Crystallography

F. Carbone,1,2 N. Gedik,1,3 J. Lorenzana,4 and A. H. Zewail1

1Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA
2 Laboratory of Ultrafast Spectroscopy, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
3MIT Department of Physics, 77 Mass. Avenue, Bldg. 13-2114 Cambridge, MA 02139, USA
4SMC-ISC-CNR, Department of Physics, Università di Roma La Sapienza, Piazzale Aldo Moro 2, 00185 Roma, Italy

Received 20 October 2009; Accepted 19 January 2010

Academic Editor: Dragan Mihailovic

Copyright © 2010 F. Carbone et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The phonon-mediated attractive interaction between carriers leads to the Cooper pair formation in conventional superconductors. Despite decades of research, the glue holding Cooper pairs in high-temperature superconducting cuprates is still controversial, and the same is true for the relative involvement of structural and electronic degrees of freedom. Ultrafast electron crystallography (UEC) offers, through observation of spatiotemporally resolved diffraction, the means for determining structural dynamics and the possible role of electron-lattice interaction. A polarized femtosecond (fs) laser pulse excites the charge carriers, which relax through electron-electron and electron-phonon couplings, and the consequential structural distortion is followed diffracting fs electron pulses. In this paper, the recent findings obtained on cuprates are summarized. In particular, we discuss the strength and symmetry of the directional electron-phonon coupling in B i 2 S r 2 C a C u 2 O 8 + 𝛿 (BSCCO), as well as the c-axis structural instability induced by near-infrared pulses in L a 2 C u O 4 (LCO). The theoretical implications of these results are discussed with focus on the possibility of charge stripes being significant in accounting for the polarization anisotropy of BSCCO, and cohesion energy (Madelung) calculations being descriptive of the c-axis instability in LCO.