| Issue |
EPL
Volume 120, Number 1, October 2017
|
|
|---|---|---|
| Article Number | 17004 | |
| Number of page(s) | 7 | |
| Section | Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties | |
| DOI | https://doi.org/10.1209/0295-5075/120/17004 | |
| Published online | 29 December 2017 | |
Effect of the next-nearest-neighbor hopping on the charge collective modes in the paramagnetic phase of the Hubbard model
Normandie Univ, ENSICAEN, UNICAEN, CNRS, CRISMAT - 14000 Caen, France
Received: 1 September 2017
Accepted: 4 December 2017
The charge dynamical response function of the 
Hubbard model is investigated on the square lattice in the thermodynamical limit. The correlation function is calculated from Gaussian fluctuations around the paramagnetic saddle-point within the Kotliar and Ruckenstein slave-boson representation. The next-nearest-neighbor hopping only slightly affects the renormalization of the quasiparticle mass. In contrast a negative 
notably decreases (increases) their velocity, and hence the zero-sound velocity, at positive (negative) doping. For low (high) density 
we find that it enhances (reduces) the damping of the zero-sound mode. Furthermore it softens (hardens) the upper-Hubbard-band collective mode at positive (negative) doping. It is also shown that our results differ markedly from the random-phase approximation in the strong-coupling limit, even at high doping, while they compare favorably with existing quantum Monte Carlo numerical simulations.
PACS: 72.15.Nj – Collective modes (e.g., in one-dimensional conductors) / 71.10.Fd – Lattice fermion models (Hubbard model, etc.) / 71.30.+h – Metal-insulator transitions and other electronic transitions
© EPLA, 2017
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