Pump-probe Auger-electron spectroscopy of Mott insulators

Article

关键词: SPECTRA;    PHOTOEMISSION;    HOLE;    BAND;    FERROMAGNETISM;    INTEGRATION;    NICKEL;   

DOI  :  10.1103/PhysRevB.99.205108

来源: SCIE

【 摘 要 】

In high-resolution core-valence-valence (CVV) Auger electron spectroscopy from the surface of a solid at thermal equilibrium, the main correlation satellite, visible in the case of strong valence-electron correlations, corresponds to a bound state of the two holes in the final state of the CVV Auger process. We discuss the physical significance of this satellite in nonequilibrium pump-probe Auger spectroscopy by numerical analysis of a single-band Hubbard-type model system, including core states and a continuum of high-energy scattering states. It turns out that the spectrum of the photo-doped system, due to the increased double occupancy, shares features with the equilibrium spectrum at higher fillings. The pumping of doublons can be watched when working with overlapping pulses at short Delta t. For larger pump-probe delays Delta t and on the typical femtosecond timescale for electronic relaxation processes, spectra are hardly Delta t dependent, reflecting the high stability of bound two-hole states for strong Hubbard U. We argue that taking into account the spatial expansion of single-particle orbitals when these are doubly occupied, as described by the dynamical Hubbard model, produces an oscillation of the barycenter of the satellite as a function of Delta t. Pump-probe Auger-electron spectroscopy is thus highly sensitive to dynamical screening of the Coulomb interaction.

【 授权许可】

Free