Regensburg 2022 – scientific programme

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MA: Fachverband Magnetismus

MA 19: Poster 1

MA 19.33: Poster

Tuesday, September 6, 2022, 17:30–20:00, P2

Moments and multiplets in moiré materials: A pseudo-fermion functional renormalization group for spin-valley models — •Lasse Gresista, Dominik Kiese, and Simon Trebst — Institute for Theoretical Physics, University of Cologne, Germany

The observation of strongly-correlated states in moiré systems has renewed the conceptual interest in magnetic systems with higher SU(4) spin symmetry, e.g. to describe Mott insulators where the local moments are coupled spin-valley degrees of freedom. In addition to possible geometrical or interaction induced frustration, the enhanced quantum fluctuations in these systems are expected to counteract the formation of magnetic order, making them prime candidates to host exotic quantum spin-valley or spin-orbital liquid ground states. A method that has demonstrated its potential to distinguish between magnetically ordered and disordered states, even in the presence of frustration and in three dimensions, is the pseudo-fermion function renormalization group (pf-FRG). In our work we generalize this method from conventional SU(2) spin models to very general spin-valley Hamiltonians, showing that it can indeed be applied to study the magnetic behavior of moiré materials. We present the quantum phase diagram of SU(2)^spin ⊗ U(1)^valley symmetric spin-valley models relevant for the strong coupling description of trilayer graphene on hexagonal boron nitride (TG/h-BN) and twisted bilayer graphene (TBG).