Title: Oral: Spectral signatures of residual electron pairing in the dilute Hubbard-Su-Schrieffer-Heeger model

Electron-phonon interactions are critical for understanding many strongly correlated systems. In this context, the SSH model, where atomic motion modulates the nearest-neighbor hopping integrals, has gained significant attention due to its potential for strong electron pairing. Introducing the Hubbard interaction (U) into the SSH model leads to a complex interplay between electron-electron (e-e) and electron-phonon (e-ph) interactions. While the Hubbard-SSH (HSSH) model has been extensively studied at half-filling and moderately doped regimes, its behavior in the low electron density limit remains largely unexplored. In this work, we investigate the spectral properties of the one-dimensional Hubbard-SSH (HSSH) model at low density using the Density Matrix Renormalization Group (DMRG) method directly in the frequency space. Our results reveal the presence of an anomalous resonance in the single-particle spectral function for specific values of electron-phonon coupling, which depends on the onsite (U), nearest-neighbor (V) Hubbard interactions, and electron density. With additional analytical calculations, we demonstrate that this anomalous spectral feature reflects the residual strong attraction between electrons mediated by the SSH interaction.