Antiferromagnetism Induced by Bond Su-Schrieffer-Heeger Electron-Phonon Coupling: A Quantum Monte Carlo Study

Antiferromagnetism (AFM) such as Neel ordering is often closely related to Coulomb interactions such as Hubbard repulsion in two-dimensional (2D) systems. Whether Neel AFM ordering in two dimensions can be dominantly induced by electron-phonon couplings (EPC) has not been completely understood. Here, by employing numerically exact sign-problem-free quantum Monte Carlo (QMC) simulations, we show that bond Su-Schrieffer-Heeger (SSH) phonons with frequency omega and EPC constant lambda can induce AFM ordering for a wide range of phonon frequency omega > omega(c). For omega < omega(c), a valence-bond-solid (VBS) order appears and there is a direct quantum phase transition between VBS and AFM phases at omega(c). The phonon mechanism of the AFM ordering is related to the fact that SSH phonons directly couple to electron hopping whose second-order process can induce an effective AFM spin exchange. Our results shall shed new light on understanding AFM ordering in correlated quantum materials.

Automated summary

The study demonstrates that SSH phonons can induce AFM ordering in two-dimensional systems, and also reveals a direct quantum phase transition between VBS order and AFM phase. The phonon mechanism of AFM ordering is attributed to SSH phonons directly coupling to electron hopping processes.