UNFOLDING THE ULTRAFAST INTERPLAY BETWEEN DELOCALIZED WAVEFUNCTIONS AND LOCALIZED ELECTRONIC INTERACTIONS IN QUANTUM CORRELATED MATERIALS
Tesi di Dottorato
Data di Pubblicazione:
2015
Citazione:
UNFOLDING THE ULTRAFAST INTERPLAY BETWEEN DELOCALIZED WAVEFUNCTIONS AND LOCALIZED ELECTRONIC INTERACTIONS IN QUANTUM CORRELATED MATERIALS / S. Peli ; tutor: C. Giannetti ; coordinatore: M. Bersanelli. UNIVERSITA' DEGLI STUDI DI MILANO, 2015 Jan 23. 27. ciclo, Anno Accademico 2014. [10.13130/peli-simone_phd2015-01-23].
Abstract:
The complex phase diagram of strongly correlated materials is regulated by the delicate interplay between the low-energy electronic excitations and those involving higher energy scales. Here we combine time-resolved optical spectroscopy, conventional laser photoemission (tr-ARPES) and XUV-laser photoemission (XUV-ARPES) to investigate, with an out-of-equilibrium approach, the high-energy electron dynamics in two families of superconducting copper oxides: the single-layer Bi2Sr2-xLaxCuO6+d (Bi2201) and double-layer Bi2Sr2Ca0.92Y0.08Cu2O8+d (Bi2212). We focused on the pump induced modification of the charge-transfer (CT) transition at >2 eV, that strongly reflects the correlation degree of the electronic wavefunction. We observe a qualitative change of the dynamics of the CT transition at T=300 K and hole doping p_cr=0.17+-0.02. We argue that the observed change at p_cr is intimately connected to the quantum critical point at T=0, from which different charge and spin ordering tendencies emerge. Furthermore, time-resolved XUV angle-resolved-photoemission experiments allowed us to track the transient occupation of both the conduction and the oxygen bands during the relaxation dynamics. Our results unveiled the different nature (bonding, non-bonding) of the oxygen bands at 1.5 eV binding energy. This is reflected in a strong bottleneck in the relaxation of the holes photoexcited in the O-2p-pi band at (pi,pi) which is non-bonding with the 3dx^2-y^2 Cu states.These results challenge the state-of-the-art models that describe the relaxation dynamics in copper oxides.
Tipologia IRIS:
Tesi di dottorato
Keywords:
strongly correlated materials; cuprates; quantum critical point; time-resolved photoemission; time-resolved spectroscopy
Elenco autori:
S. Peli
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