The electron–lattice interaction gives rise to a rich set of phenomena in quantum materials. Microscopically, this interaction often arises from the modulation of orbital overlaps; however, many theoretical studies neglect such couplings. Here, we present an exact diagonalization and determinant quantum Monte Carlo study of a three-orbital Su–Schrieffer–Heeger (SSH) model, on a two-dimensional Lieb lattice and in the negative charge transfer regime. At half-filling (one hole/unit cell), we observe a bipolaron insulating phase with a bond-disproportionate lattice. This phase is robust against moderate hole doping but is suppressed at large hole concentrations, leading to a metallic polaron-liquid-like state with fluctuating patches of local distortions. We also find an s-wave superconducting state at large hole doping that primarily appears on the oxygen sublattice. Our work provides a non-perturbative view of SSH-type couplings in two dimensions with implications for materials where such couplings are dominant.

电子-晶格相互作用在量子材料中引起了一系列丰富的现象。在微观上，这种相互作用通常是由轨道重叠的调制引起的。但是，许多理论研究忽略了这种耦合。在这里，我们介绍了二维利布晶格和负电荷转移机制下三轨道Su–Schrieffer–Heeger（SSH）模型的精确对角化和行列式量子蒙特卡洛研究。在半填充时（一个孔/单位晶胞），我们观察到一个双极性绝缘相具有键不成比例的晶格。该相对中等程度的空穴掺杂具有鲁棒性，但在大的空穴浓度下会被抑制，从而导致金属极化子液体状的状态，并具有局部畸变的波动。我们还发现一个小号在大空穴掺杂处的波超导状态主要出现在氧亚晶格上。我们的工作提供了二维的SSH型耦合器的非扰动性视图，暗示了此类耦合器占主导地位的材料。