Robustness of Antiferromagnetism in the Su-Schrieffer-Heeger-Hubbard model

TL;DR

This paper uses large-scale quantum Monte Carlo simulations to explore how electron-phonon coupling and Hubbard interactions jointly influence antiferromagnetism in the SSHH model, revealing that Hubbard interactions enhance EPC-induced AFM especially in certain regimes.

Contribution

It provides the first comprehensive ground-state phase diagram of the SSHH model showing the cooperative enhancement of AFM by Hubbard interactions and EPC, beyond conventional understanding.

Findings

Hubbard interactions enhance EPC-induced AFM.

AFM is most enhanced at small phonon frequencies.

Results are relevant to understanding quantum materials.

Abstract

We recently unveiled that antiferromagnetism (AFM) order can be dominantly induced by the bond Su-Schrieffer-Heeger (SSH) electron-phonon coupling (EPC), which is beyond the conventional wisdom that AFM order is usually driven by strong Coulomb interactions. Nevertheless, many aspects of the interplay between EPC and strong electronic interactions on AFM ordering remains unexplored. Here, we investigate the Su-Schrieffer-Heeger-Hubbard (SSHH) model with bond SSH phonons and onsite Hubbard interactions by large-scale quantum Monte-Carlo (QMC) simulations and obtain its ground-state phase diagram for various Hubbard interactions and EPC strength at half filling. Our results show that Hubbard interactions further enhance EPC-induced AFM, especially for small phonon frequency or in adiabatic limit, the regime most relevant to various quantum materials. This could shed further light to understanding the cooperative effect between EPC and electronic correlations in quantum materials.