Dynamics and stability of U(1) spin liquids beyond mean-field theory: Triangular-lattice $J_1$-$J_2$ Heisenberg model

Abstract

Quantum spin liquids (QSLs) are long-range entangled phases of frustrated magnets exhibiting fractionalized spin excitations. In two dimensions, there is limited analytical understanding of their excitation spectra beyond parton mean-field theories, which fail to capture many features of the finite frequency dynamical response from recent experimental and numerical works. We use a self-consistent random phase approximation (RPA) for the $J_1$-$J_2$ Heiseneberg model on the triangular lattice to describe the strong spinon-spinon interactions of the U(1) Dirac QSL. We obtain quantitative results for the dynamical spin structure factor and phase diagram compatible with comprehensive numerical efforts. We extend the method to chiral QSLs, and discuss its broad range of applicability to other models and for describing inelastic neutron scattering experiments.