Real-Time Observation of Cuprates Structural Dynamics by Ultrafast Electron Crystallography
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 Bi_2Sr_2CaCu_2O_(8+δ) (BSCCO), as well as the c-axis structural instability induced by near-infrared pulses in La_2CuO_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.
Additional InformationCopyright © 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. Received 20 October 2009; Accepted 19 January 2010. Academic Editor: Dragan Mihailovic. This work was supported by the National Science Foundation and the Air Force Office of Scientific Research in the Gordon and Betty Moore Center for Physical Biology at Caltech. The authors acknowledge stimulating discussions with Professor Z. X. Shen, Professor A. Georges, Dr. Th. Jarlborg, Dr. A. Kuzmenko, Dr. E. Giannini, and Professor D. van der Marel. Dr. F. Carbone acknowledges the support from the Suisse National Science Foundation through an Ambizione grant.
Published - Carbone2010Adv_Cond_Matt_Phys.pdf