Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 2: SC: Properties, Electronic Structure, Mechanisms 1
TT 2.2: Talk
Monday, March 14, 2011, 10:45–11:00, HSZ 301
Momentum-Resolved Ultrafast Electron Dynamics in Superconducting Bi2Sr2CaCu2O8+δ — •L. Rettig1,2, R. Cortes1,3, Y. Yoshida4, H. Eisaki4, M. Wolf3, and U. Bovensiepen2 — 1Fachb. Physik, Freie Univ. Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Fak. f. Physik, Univ. Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany — 3Abt. Phys. Chemie, Fritz-Haber-Institut d. MPG, Faradayweg 4-6, 14195 Berlin, Germany — 4Nat. Inst. of Adv. Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
The processes responsible for the relaxation of hot quasiparticles (QPs) in high-Tc superconductors have been intensely studied by time-resolved optical and THz spectroscopy. These studies conclude on highly momentum dependent dynamics, which however cannot be resolved directly by these momentum integrating techniques.
Here, we report on the non-equilibrium state of the high-Tc superconductor Bi2Sr2CaCu2O8+δ and its ultrafast dynamics investigated by femtosecond time- and angle-resolved photoemission spectroscopy. This technique allows direct investigation of excited QPs and the dynamics of the superconducting state with both momentum and energy resolution. Thus, we are able to investigate optically excited QPs at different electron momenta along the Fermi surface and detect metastable QPs near the antinode. Their decay through e-e scattering is blocked by a scattering phase space restricted to the nodal region. We find a single exponential relaxation of the excited QPs with momentum independent decay rates, in agreement with relaxation dominated by Cooper pair recombination in a boson bottleneck limit.