Quantum disordered state of magnetic charges in nanoengineered honeycomb lattice*

A quantum magnetic state due to magnetic charges is never observed, even though they are treated as quantum mechanical variables in theoretical calculations. Here, the occurrence of a novel quantum disordered state of magnetic charges in a nanoengineered magnetic honeycomb lattice of ultra-small connecting elements is demonstrated. A magnetic honeycomb lattice with competing exchange interactions between Ising moments is theoretically predicted to exhibit disordered magnetic states with macroscopic degeneracy. The experimental research, performed using spin-resolved neutron scattering, reveals a robust massively degenerate ground state, comprised of low integer and energetically forbidden high integer magnetic charges, that manifests cooperative paramagnetism at low temperature. We explored the competing physics of energy vs. entropy in a thermally tuned magnetic phase transition. The system tends to preserve the degenerate configuration even under large magnetic field applications. It exemplifies the robustness of the disordered correlation of magnetic charges in a 2D honeycomb lattice. The realization of a quantum disordered ground state elucidates the dominance of exchange energy, which is enabled due to the nanoscopic magnetic element size in nanoengineered honeycomb. Consequently, an archetypal platform is envisaged to study quantum mechanical phenomena due to emergent magnetic charges.