Speaker
Stefano Dal Conte
(Eindhoven University of Technology)
Description
S. Dal Conte1,2, C. Giannetti3, G. Coslovich4,5, F. Cilento4, D. Bossini3,6, T. Abebaw4, F. Banfi3, G. Ferrini3, H. Eisaki7, M. Greven8, A. Damascelli9,10, D. van der Marel11 & F. Parmigiani4,12
1 Department of Physics A. Volta, Universit`a degli Studi di Pavia, Pavia I-27100, Italy.
2 Present address: Physics Department, Eindhoven University of Technology, the Netherlands.
3 Department of Physics, Universit`a Cattolica del Sacro Cuore, Brescia I-25121, Italy.
4 Department of Physics, Universit`a degli Studi di Trieste, Trieste I-34127, Italy.
5 Present address: Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, CA 94720, USA.
6 Present address: Institute forMolecules andMaterials, Radboud University Nijmegen, the Netherlands.
7 Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan.
8 School of Physics and Astronomy, University of Minnesota, Minneapolis,Minnesota 55455, USA
9 Department of Physics & Astronomy, University of British Columbia, Vancouver, Canada.
10 Quantum Matter Institute, University of British Columbia, Vancouver, Canada.
11 D´epartement de Physique de la Mati`ere Condens´ee, Universit´e de Gen`eve, Switzerland.
12 Sincrotrone Trieste S.C.p.A., Basovizza I-34012, Italy.
The mechanism behind the formation of Cooper pairs in high-Tc superconductors is a subject of strong debate. In particular the research narrows down to two mechanisms: phonons and excitations of electronic origin are both considered the main candidates of the pairing mechanism in these compounds. Experiments performed at equilibrium conditions have the capability to reconstruct the glue spectrum. On the contrary they are insensitive to the nature of the glue and failed to separate these two contributions as they could coexist on the same energy scale (<100 meV).
Here we tackle this problem by measuring the optical response of a Bi2Sr2Ca0.92Y0.08Cu2O8+d crystal on both time and frequency domains[1]. By fitting the experimental data to the calculated variation of reflectivity at different delay times, we are able to unambiguously disentangle the electronic and phononic contribution of the glue on the basis of their different temporal dynamics[2]. We find that, on the time scale faster than electron-phonon thermalization, the quasiparticles are already thermalized with the excitations of electronic origin participating to the glue. The strength of this interaction (lambda∼1.1) fully accounts for the high critical temperature of the system. These results represent an important step ahead in the understanding of the pairing mechanism in cuprates and pave the way for the investigation of the electron-boson coupling in a variety of complex materials, ranging from transition-metal oxides to iron-based superconductors.
[1] Monthoux et al. Superconductivity without phonons. Nature 450, 1177 (2007).
[2] Kresin et al. Colloquium: Electron-lattice interaction and its impact on high Tc superconductivity. Rev. Mod. Phys. 81, 481 (2009).
[3] C. Giannetti et al. Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates. Nature Communications 2, 353 (2011).
[4] S. Dal Conte et al. Disentangling the electronic and phononic glue in a high-Tc superconductor. Science, in press.
Primary author
Stefano Dal Conte
(Eindhoven University of Technology)
