Noncoplanar orders and quantum disordered states in maple-leaf (anti)ferromagnets

Abstract

A promising route towards the realization of chiral spin liquids is the quantum melting of classically noncoplanar spin states via quantum fluctuations. In the classical realm, such noncoplanar orders can effectively be stabilized by interactions beyond nearest neighbors. Motivated by the recent synthesis of materials with a maple-leaf lattice geometry, we study the effect of cross-plaquette couplings on elementary Heisenberg antiferromagnets for this geometry (as well as their ferromagnetic counterparts). We find a rich spectrum of noncoplanar states, including a novel icosahedral order as well as incommensurate spin spirals, using large-scale Monte Carlo simulations in combination with a semi-analytical analysis. To inspect the potential quantum melting of these states, we analyze the quantum $S = 1/2$ variant of these models using pseudo-fermion functional renormalization group (pf-FRG) simulations. Notably, we indeed find extended parameter regimes lacking long-range magnetic order -- in regions classically occupied by noncoplanar orders -- which we putatively identify with the possible formation of chiral quantum spin liquids.