arXiv subjects

Loïc Philoxene

Publications and source records attributed to Loïc Philoxene.

3 recordsLinked to original sources

arXiv2024

Charge Collective Modes in Correlated Electron Systems: Plasmons Beyond the Random Phase Approximation

Elucidating the impact of strong electronic interactions on the collective excitations of metallic systems has been of longstanding interest, mainly due to the inadequacy of the random phase approximation (RPA) in the strongly correlated regime. Here, we adopt our newly developed radial Kotliar and Ruckenstein slave boson representation to analyze the charge excitation spectrum of a Hubbard model, extended with long range interactions. Working on the face centered cubic lattice, at half filling, and in different coupling regimes ranging from uncorrelated to the metal-to-insulator transition, we compare our results to conventional RPA as a benchmark. We focus on the influence of the local and long range couplings on the particle-hole excitation continuum and the plasmon and upper Hubbard band collective modes. Beyond the weak coupling regime, we find numerous quantitative and even qualitative discrepancies between our method and standard RPA. Our work thus deepens the understanding of charge collective modes in correlated systems, and lays the foundations for future studies of a broad series of materials.

cond-mat.str-el↗

arXiv2023

Phase coexistence in a half-filled extended Hubbard model

In this Letter we analyze the coexisting ordered phases that arise in the half-filled $\varepsilon$-t-U-V extended Hubbard Model on the square lattice when tackled within the Kotliar andRuckenstein slave boson representation in the thermodynamical limit. Particular emphasis is put on the dependence of the quasiparticle dispersions, the gaps, the spin-resolved renormalization factors, and the distribution of double occupancy on the microscopical parameters of the model. Our calculations are performed in a parameter range that is most suitable for resistive switching. In particular, the main contributions to the gaps are shown to either arise from $\varepsilon$ in the weak coupling regime, or from U and V when they are the largest scales. The gaps are thus from joint spin and charge origin, and so are the order parameters.

cond-mat.str-el↗

arXiv2023

Spin and charge modulations of a half-filled extended Hubbard model

We introduce and analyze an extended Hubbard model, in which intersite Coulomb interaction as well as a staggered local potential (SLP) are considered, on the square lattice at half band filling, in the thermodynamic limit. Using both Hartree-Fock approximation and Kotliar and Ruckenstein slave boson formalism, we show that the model harbors charge order (CO) as well as joint spin and charge modulations (SCO) at finite values of the SLP, while the spin density wave (SDW) is stabilized for vanishing SLP, only. We determine their phase boundaries and the variations of the order parameters in dependence on the SLP, as well as on the on-site and nearest-neighbor interactions. Domains of coexistence of CO and SCO phases, suitable for resistive switching experiments, are unraveled. We show that the novel SCO systematically turns into the more conventional SDW phase when the zero-SLP limit is taken. We also discuss the nature of the different phase transitions, both at zero and finite temperature. In the former case, no continuous CO to SDW (or SCO) phase transition occurs. In contrast, a paramagnetic phase (PM), which is accompanied with continuous phase transitions towards both spin or charge ordered phases, sets in at finite temperature. A good quantitative agreement with numerical simulations is demonstrated, and a comparison between the two used approaches is performed.

cond-mat.str-el↗