Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 39: Correlated Electrons: Charge Order
TT 39.5: Talk
Friday, September 9, 2022, 12:15–12:30, H23
Charge-density waves in Kagome-lattice extended Hubbard models at the van Hove filling — •Francesco Ferrari1, Federico Becca2, and Roser Valentí1 — 1Goethe University, Frankfurt am Main, Germany — 2University of Trieste, Trieste, Italy
The Hubbard model on the kagome lattice is presently often considered as a minimal model to describe the rich low-temperature behavior of AV3Sb5 compounds (with A=K, Rb, Cs), including charge-density waves (CDWs), superconductivity, and possibly broken time-reversal symmetry. We investigate, via variational Jastrow-Slater wave functions, the properties of its ground state when both onsite U and nearest-neighbor V Coulomb repulsions are considered at the van Hove filling. Our calculations reveal the presence of different interaction-driven CDWs and, contrary to previous renormalization-group studies, the absence of ferromagnetism and charge- or spin-bond order. No signatures of chiral phases are detected. Remarkably, the CDWs triggered by the nearest-neighbor repulsion possess charge isproportionations that are not compatible with the ones observed in AV3Sb5. As an alternative mechanism to stabilize charge-bond order, we consider the electron-phonon interaction, modeled by coupling the hopping amplitudes to quantum phonons, as in the Su-Schrieffer-Heeger model. Our results show the instability towards a tri-hexagonal distortion with 2x2 periodicity, in a closer agreement with experimental findings.