| The properties of condensed matter are determined by single-particle and collective excitations and their mutual interactions. The coupling of excitations may lead to abrupt changes ("kinks") in the slope of the electronic dispersion. Kinks thus carry important information about internal degrees of freedom of a many-body system and their effective interaction. Here we report a novel, purely electronic mechanism leading to kinks, which is not related to any coupling of excitations. Namely, kinks are predicted for any strongly correlated metal whose spectral function shows a three-peak structure with well-separated Hubbard subbands and central peak, as observed, for example, in transition metal-oxides. These kinks can appear at energies as high as a few hundred meV, as found in recent spectroscopy experiments on high-temperature superconductors and other transition-metal oxides. Our theory determines not only the position of the kinks but also the range of validity of Fermi-liquid theory. |
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