Related Experiment Video
Updated: Sep 7, 2025

Optimized Fabrication Procedure for High-Quality Graphene-based Moiré Superlattice Devices
Published on: July 11, 2025
SU(4) Symmetry in Twisted Bilayer Graphene: An Itinerant Perspective
Dmitry V Chichinadze1, Laura Classen2, Yuxuan Wang3
1School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Abstract:
We study symmetry-broken phases in twisted bilayer graphene at small filling above charge neutrality and at van Hove filling. We argue that the Landau functionals for the particle-hole order parameters at these fillings both have an approximate SU(4) symmetry, but differ in the sign of quartic terms. We determine the order parameter manifold of the ground state and analyze its excitations. For small fillings, we find a strong first-order transition to an SU(3)⊗U(1) manifold of orders that break spin-valley symmetry and induce a 3-1 splitting of fermionic excitations. For van Hove filling, we find a weak first-order transition to an SU(2)⊗SU(2)⊗U(1) manifold of orders that preserves the twofold band degeneracy. We discuss the effect of particle-hole orders on superconductivity and compare with strong-coupling approaches.
Related Concept Videos
VSEPR Theory and the Effect of Lone Pairs
Gauss's Law: Planar Symmetry
Unsymmetric Bending
Structure of Benzene: Molecular Orbital Model
Hybridization of Atomic Orbitals I
Conformations of Cyclohexane
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...

