Regensburg 2025 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 7: Correlated Electrons: Electronic Structure Calculations
TT 7.8: Talk
Monday, March 17, 2025, 17:00–17:15, H31
Non-flat bands and chiral symmetry in magic angle twisted bilayer graphene — •Miguel Sánchez1, José González2, and Tobias Stauber1 — 1Insituto de Ciencia de Materiales de Madrid ICMM-CSIC. Madrid, Spain — 2Insituto de Estrrcutura de la Materia IEM-CSIC. Madrid, Spain)
We find that in any effective theory of magic angle twisted bilayer graphene (MATBG) that integrates out high-energy modes, the flat bands are prone to a significant increase in bandwidth. This effect from the Coulomb interaction is comparable to and even exceeding the perturbations due to strain and electron-phonon coupling.
As a result of this band widening, we identify a pattern of explicit symmetry breaking in MATBG from the ideal U(4) × U(4) symmetry down to the chiral non-flat U(4) group, in contrast to the flat U(4) symmetry that prevails when the bands are very flat.
Our work builds upon and extends a previous study [1]. For instance, we employ an atomistic model of MATBG that treats the full bandwidth accurately. Moreoever, we discuss the implications of our results for the latest experimental and theoretical findings.
[1] Phys. Rev. Lett. 125, 257602 (2020).
Keywords: Twisted bilayer graphene; Flat bands; Hartree-Fock theory; Effective models