The electron-phonon coupling in cuprates by fs electron diffraction

by Prof. Fabrizio Carbone

Thursday 25 Jun 2009, 15:00 → 16:00 Europe/Rome

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

Ultrafast light pulses can abruptly drive a solid out of equilibrium. In particular, a large temperature difference between light charge carriers and heavy ions can be induced. This unbalance is restored through heat transfer between electrons and lattice, governed by electron-phonon coupling. Time-resolved optical techniques have been widely used in order to estimate this important parameter, by measuring the relaxation of carrier excitation. In time-resolved electron crystallography, the electronic structure is excited through light, and the dynamic crystal structure obtained in diffraction provides directly th! e lattice temperature as well as the strength and symmetry of the electron-phonon coupling parameter. We apply this technique to cuprates superconductors, and observe that the coupling between carriers excited by polarized light and the structure is anisotropic. The implications of these observations in terms of the pairing mechanism in cuprates are discussed.