A Scaling Theory for ac Magnetic Response in Kagome Ice

A theory for frequency-dependent magnetic susceptibility \chi(\omega) is developed for thermally activated magnetic monopoles in kagome ice. By mapping this system to a two-dimensional (2D) Coulomb gas and then to a sine-Gordon model, we have shown that the susceptibility has a scaling form \chi(\omega)/\chi(0)={\cal F}(\omega/\omega_1), where the characteristic \omega_1 is related to a charge correlation length between diffusively moving monopoles, and to the sine-Gordon principal breather. The dynamical scaling is universal among superfluid and superconducting films, and 2D XY magnets above Kosterlitz-Thouless transitions.