Semiclassical approach to quantum spin ice

We propose a semiclassical description of the low-energy properties of quantum spin ice in the strong Ising limit. Within the framework of a semiclassical, perturbative Villain expansion, that can be truncated at arbitrary order, we give an analytic and quantitative treatment of the deconfining phase. We find that photon-photon interactions significantly renormalize the speed of light and split the two transverse photon polarizations at intermediate wave vectors. We calculate the photon velocity and the ground-state energy to first and second order in perturbation theory, respectively. Both are in good agreement with recent numerical simulations. We further compute the classical energy of the vison excitation.