Quantum and Classical Phases of the Pyrochlore Heisenberg Model with Competing Interactions

We investigate the quantum Heisenberg model on the pyrochlore lattice for a generic spin S in the presence of nearest-neighbor J1 and second-nearest-neighbor J2 exchange interactions. By employing the pseudofermion functional renormalization group method, we find, for S=1/2 and S=1, an extended quantum-spin-liquid phase centered around J2=0, which is shown to be robust against the introduction of breathing anisotropy. The effects of temperature, quantum fluctuations, breathing anisotropies, and a J2 coupling on the nature of the scattering profile, and the pinch points, in particular, are studied. For the magnetic phases of the J1-J2 model, quantum fluctuations are shown to renormalize phase boundaries compared to the classical model and to modify the ordering wave vectors of spiral magnetic states, while no new magnetic orders are stabilized.