We characterize gap-opening mechanisms in the topological heavy fermion (THF) model of magic-angle twisted bilayer graphene (MATBG), with and without electron-phonon coupling, using dynamical mean-field theory (DMFT) with the numerical renormalization group (NRG) impurity solver. In the presence of symmetry breaking associated with valley-orbital ordering (time-reversal-symmetric or Kramers intervalley coherent, or valley polarized), spin anti-Hund and orbital-angular-momentum Hund couplings, induced by the dynamical Jahn-Teller effect, result in a robust pseudogap at filling 2≲∣ν∣≲2.5. We also find that Hundness enhances the pairing susceptibilities for 1.6≲∣ν∣≲2.8, which might be a precursor to the superconducting phases neighboring ∣ν∣=2.
@article{arxiv.2412.03108,
title = {Hundness in twisted bilayer graphene: correlated gaps and pairing},
author = {Seongyeon Youn and Beomjoon Goh and Geng-Dong Zhou and Zhi-Da Song and Seung-Sup B. Lee},
journal= {arXiv preprint arXiv:2412.03108},
year = {2024}
}