Excitons, bound pairs of electrons and holes, shape how 2D materials absorb and emit light, but calculating them in quasicrystals and super-moiré structures is formidable because of the enormous size of the problem. QMAT researchers at Aalto University and a colleague at Utrecht University have developed a tensor-network method for the real-space Bethe–Salpeter Hamiltonian that reaches an excitonic Hamiltonian of 10¹⁸ dimensions.

The method computes bound-exciton spectra for systems exceeding one billion lattice sites, several orders of magnitude beyond conventional approaches, without ever storing the Hamiltonian explicitly. It resolves atomistic and mesoscopic structure at once, revealing exciton minibands and moiré-induced confinement. The authors are Anouar Moustaj, Yitao Sun, Tiago Antão and Jose Lado of the Correlated Quantum Materials group, with Lumen Eek of Utrecht University.

The preprint has not yet been peer reviewed.

Image: QMAT