Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 37: Correlated Electrons: Poster
TT 37.42: Poster
Wednesday, March 19, 2025, 15:00–18:00, P4
The Interplay Between Diagonal and Off-Diagonal Electron-Phonon Coupling in two-dimensional systems — •jadson lucas portela e silva1,2, gabriel rein2, sebastião a. s. júnior1, willdauany c. f. da silva1, fakher f. assaad2, and natanael c. costa1 — 1instituto de física universidade federal do rio de janeiro, rio de janeiro, brasil — 2institut für theoretische physik und astrophysik, universität würzburg, würzburg, germany
The interplay between diagonal and off-diagonal electron-phonon coupling in two-dimensional systems is explored using the Holstein-Su-Schrieffer-Heeger (HSSH) model through non-perturbative Monte Carlo simulations on a square lattice at half-filling. Electron-phonon coupling is crucial in determining exotic phases like charge-density waves (CDW), valence bond solids (VBS), and superconductivity. The HSSH model uniquely combines features of the Holstein and SSH models, where the former modulates the on-site potential energy, and the latter modifies the electron's kinetic energy through lattice displacements. The study constructs phase diagrams by analyzing charge-charge, bond-bond, and pairing correlation functions. Key findings include a competition between CDW and VBS phases, similar to one-dimensional systems. However, unlike the 1D case, no metallic phase is observed between these states, likely due to perfect nesting and van Hove singularities in the density of states, which destabilize the Fermi liquid state. Further exploration beyond half-filling shows that melting of CDW and VBS phases leads to superconductivity.
Keywords: electron-phonon coupling; charge-density wave; valence bond solid; Holstein model; Su-schrieffer-heeger model