Event Details

Speaker: László Oroszlány, Eötvös Loránd University, Hungary

Haldane conjectured that spin-1 chains possess an excitation gap as opposed to their spin-1/2 counterparts highlighted an essential difference of these systems. The AKLT construction gives an exactly solvable example realising the Haldane phase. In my talk I present two microscopic routes to spin-1 physics. In graphene triangulene chains, Lieb’s theorem yields robust local (S=1) moments. I will show how the effective bilinear-biquadratic spin model can be extracted from density-functional theory, and how closely the results match the experimental analysis of Mishra et al. (Nature 598, 287 (2021)). I will then discuss half-filled Hubbard tripods in quantum-dot arrays. In that setting, exact diagonalization and perturbation theory lead to an effective spin-1 description and reveal coupling geometries that can realise the AKLT ground state. My talk is based on two recent manuscripts Phys. Rev. B 107, 035432 (2023) and https://arxiv.org/abs/2603.06455.