Low and higher energy quasiparticle excitations in high-Tc superconductors
Zusammenfassung der Projektergebnisse
Within this project we have continued a long-standing and acknowledged cooperation with the Solid State Theory group of the department of Physics at the University of Rome ’La Sapienza’. Summarizing the essential results for the subproject on fluctuating charge-density waves we have detailed our understanding the spectral properties of cuprate superconductors by introducing two phenomenological schemes which can account for the dichotomy between low energy ’unperturbed’ quasiparticles and high energy charge (and spin) order as indicated by scanning tunneling microscopy and ARPES experiments. Within this framework we have obtained the non trivial result that upon increasing (binding) energy, a large Fermi surface gradually evolves into a “segment-like” energy profile typical of well-formed stripes and, at even larger energies, into hole pockets typical of a antiferromagnetically ordered state. This result clearly captures the physical idea of slowly fluctuating charge collective modes, and more fastly fluctuating spin degrees of freedom. Concerning the second subproject, the finding of a correlation-induced enhancement of the (transitive) electron phonon interaction is apparently not followed by a similar enhancement of the overall influence of phonons on superconductivity. Similar to local (Holstein-type couplings) the impact of phonons on superconductivity is suppressed by the Coulomb interactions. This is because in our model the enhancement happens in a channel that is not beneficial for d-wave superconductivity, namely A1g, and also because it happens in a restricted momentum range. Notwithstanding the effect on superconductivity, there may be a larger impact on other properties which are more sensitive to the local, rather than the global, momentum dependence like the appearance of kinks on the electron dispersion due to self-energy effects. Also the enhancement of the scattering function at small momentum plays an important role in phase separation instabilities. Finally, our results for pair excitations in cuprates, obtained within the time-dependent Gutzwiller approximation, suggest to measure selective Auger processes in the copper and oxygen channels whose intensity allows for a measure of the correlation strength in these materials. The results here obtained within the three-band model might help to assign the unrelaxed features of Auger photoelectron coincidence spectroscopy both for electron and hole doped cuprates. Since the antibound peaks shift significantly with respect to the chemical potential it would be very interesting to study the doping dependence. We expect that such experimental and theoretical studies, accessible to the current state of the art, will make Auger spectroscopy a much more useful tool than before, for the study of partially filled correlated systems.
Projektbezogene Publikationen (Auswahl)
- Dynamical charge and spin density wave scattering in cuprate superconductors. New Journal of Physics 12, 105010 (2010)
G. Seibold, M. Grilli, and J. Lorenzana
- Particle-particle response function as a probe for electronic correlations in the p-d Hubbard model. Phys. Rev. B 82, 075137 (2010)
S. Ugenti, M. Cini, G. Seibold, J. Lorenzana, E. Perfetto, and G. Stefanucci
- Phonon renormalization from local and transitive electron-lattice couplings in strongly correlated systems. Phys. Rev. B 81, 155116 (2010)
E. von Oelsen, A. Di Ciolo, J. Lorenzana, G. Seibold, and M. Grilli
- Influence of correlations on transitive electron-phonon couplings in cuprate superconductors. Phys. Rev. B 83, 174522 (2011).
G. Seibold, M. Grilli, and J. Lorenzana
- Stripes in cuprate superconductors: Excitations and dynamic dichotomy. Physica C 481, 132 (2012)
G. Seibold, M. Grilli, and J. Lorenzana
- Linear-Response Dynamics from the Time-Dependent Gutzwiller Approximation. New Journal of Physics 15 053050 (2013)
J. Bünemann, M. Capone, J. Lorenzana, G. Seibold
(Siehe online unter https://doi.org/10.1088/1367-2630/15/5/053050)
