paper

Resonating Valence Bond States in an Electron-Phonon System

arXiv:2210.16321 · doi:10.1103/PhysRevLett.130.186404

Abstract

We study a simple electron-phonon model on square and triangular versions of the Lieb-lattice using an asymptotically exact strong coupling analysis. At zero temperature and electron density (one electron per unit cell), for various ranges of parameters in the model, we exploit a mapping to the quantum dimer model to establish the existence of a spin-liquid phase with topological order (on the triangular lattice) and a multi-critical line corresponding to a quantum critical spin liquid (on the square lattice). In the remaining part of the phase diagram, we find a host of charge-density-wave phases (e.g. valence-bond crystals), a conventional s-wave superconducting phase, and with the addition of a small Hubbard to tip the balance, a phonon-induced d-wave superconducting phase. Under a special condition, we find a hidden pseudo-spin symmetry that implies an exact constraint on the superconducting order parameters.

The title is changed from "Resonating Valence Bond States and other surprises in an Electron-Phonon System"

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