We investigate the normal state of the ''11'' iron-based superconductor FeSe 0:42 Te 0:58 by angle-resolved photoemission. Our data reveal a highly renormalized quasiparticle dispersion characteristic of a strongly correlated metal. We find sheet dependent effective carrier masses between %3 and 16m e corresponding to a mass enhancement over band structure values of m à =m band % 6-20. This is nearly an order of magnitude higher than the renormalization reported previously for iron-arsenide superconductors of the ''1111'' and ''122'' families but fully consistent with the bulk specific heat.

We explore the interplay of electron-electron correlations and spin-orbit coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved photoemission spectroscopy. Our precise measurement of the Fermi surface confirms the importance of spin-orbit coupling in this material and reveals that its effective value is enhanced by a factor of about two, due to electronic correlations. The self-energies for the β and γ sheets are found to display significant angular dependence. By taking into account the multi-orbital composition of quasiparticle states, we determine self-energies associated with each orbital component directly from the experimental data. This analysis demonstrates that the perceived angular dependence does not imply momentum-dependent many-body effects, but arises from a substantial orbital mixing induced by spin-orbit coupling. A comparison to single-site dynamical mean-field theory further supports the notion of dominantly local orbital self-energies, and provides strong evidence for an electronic origin of the observed non-linear frequency dependence of the self-energies, leading to 'kinks' in the quasiparticle dispersion of Sr2RuO4. * present address: ISIS Facility, Rutherford

We present a quantum-kinetic theory of the excitation transfer in a quantum dot molecule. We derive the consistent Markovian limit for the system kinetics, which leads to a description in terms of a single transfer rate for weak coupling. We show that the transfer rate is a strongly varying, nonmonotonic function of the spatial separation and energy mismatch between the dots.

We present angle-resolved photoemission data from Cu(111). Using a focused 6 eV continuous-wave laser for photoexcitation, we achieve a high effective momentum resolution, enabling detection of the Rashba spin splitting in the Shockley surface state on Cu(111). The magnitude of the spin splitting of k ∼ 0.006Å −1 is surprisingly large and exceeds values predicted for the analogous surface state on Ag(111), but is reproduced by first-principles calculations. We further resolve a kink in the dispersion, which we attribute to electron-phonon coupling.