Showing papers by "Claudio Giannetti published in 2011"
TL;DR: The interplay between the many-body high-energy CuO2 excitations at 1.5 and 2 eV, and the onset of HTSC is reported, revealing an unconventional mechanism both below and above the optimal hole concentration required to attain the maximum critical temperature (Tc).
Abstract: In strongly correlated systems the electronic properties at the Fermi energy (EF) are intertwined with those at high-energy scales. One of the pivotal challenges in the field of high-temperature superconductivity (HTSC) is to understand whether and how the high-energy scale physics associated with Mott-like excitations (|E−EF|>1 eV) is involved in the condensate formation. Here, we report the interplay between the many-body high-energy CuO2 excitations at 1.5 and 2 eV, and the onset of HTSC. This is revealed by a novel optical pump-supercontinuum-probe technique that provides access to the dynamics of the dielectric function in Bi2Sr2Ca0.92Y0.08Cu2O8+δ over an extended energy range, after the photoinduced suppression of the superconducting pairing. These results unveil an unconventional mechanism at the base of HTSC both below and above the optimal hole concentration required to attain the maximum critical temperature (Tc).
106 citations
TL;DR: In this paper, the authors report extensive ultrafast time-resolved reflectivity experiments on overdoped Bi-Sr and Ca-Ca single crystals, showing a lack of the quasiparticle decay time divergence at the fluence required to induce photoinduced phase transition.
Abstract: Here we report extensive ultrafast time-resolved reflectivity experiments on overdoped Bi${}_{2}$Sr${}_{2}$Ca${}_{1\ensuremath{-}x}$Y${}_{x}$Cu${}_{2}$O${}_{8+\ensuremath{\delta}}$ single crystals ($T$${}_{c}=78$ K) aimed to clarify the nature of the superconducting-to-normal-state photoinduced phase transition. The data show a lack of the quasiparticle decay time divergence at the fluence required to induce this phase transition, in contrast to the thermally driven phase transition observed at $T$${}_{c}$ and at variance with recently reported photoinduced transitions from charge-density and spin-density waves to a metal. Our data demonstrate the nonthermal character of the superconducting-to-normal-state photoinduced phase transition. The data are analyzed using an ad-hoc time-dependent Rothwarf-Taylor model, opening the question of the order of this nonequilibrium phase transition.
30 citations
TL;DR: In this paper, an experimental proof of the correlation among local structure and second harmonic generation in bulk nanostructured potassium niobiosilicate (KNS) glasses is presented and discussed.
Abstract: This communication presents and discusses an experimental proof of the correlation among local structure and second harmonic generation (SHG) in bulk nanostructured potassium niobiosilicate (KNS) glasses. In particular, SHG shows a maximum in correspondence of the early stages of nanostructuring, that are characterized by the segregation within the amorphous matrix of nanosized inhomogeneities. EXAFS experiments indicate that these inhomogeneities are determined by the maximum size reached by the niobium second coordination shell combined with the sudden inclusion of potassium atoms in it. Such rearrangement at the local level determines the maximum fluctuation of the bulk glass refractive index and in turn its maximum SHG activity.
6 citations