Semiclassical approach to partial magnetic order in Kondo lattices

Using the combination of a new effective Hamiltonian approach and hybrid Monte Carlo simulations, we unveil a variety of partially magnetically ordered (PMO) phases in the Kondo lattice model. Our approximation is motivated by two crucial features of the Hamiltonian: (i) formation of Kondo singlets leading to vanishing local magnetic moments, and (ii) spatially correlated nature of the effective single-particle kinetic energy. We discover PMO phases with fractional values $1/4$, $3/8$, and $1/2$ of Kondo-screened sites. A common understanding of these states emerges in terms of a nonlocal ordering mechanism. Our semiclassical approach can be generalized to study other interacting quantum systems in the intermediate coupling regime.