Single (spinor) particle motions in randomly fluctuating U(1) and SU(2) magnetic fluxes in two dimensions are compared. While the problems are similar in the weak-fluctuation limit, strikingly different physical behavior is found in the strong-fluctuation limit. The orbital susceptibility with respect to an external magnetic field vanishes in the strong-coupling U(1) limit, while in the SU(2) case a finite paramagnetic response exists, with an effective coupling constant 2e. Potential applications of the results to spin liquids and other problems are discussed.

• Received 17 December 1993

DOI:https://doi.org/10.1103/PhysRevB.49.13263