Superfluid-insulator transition of the two-dimensional fully-frustrated quantum rotor model in the spherical limit

We study the critical properties of the superfluid-insulator transition in the fully-frustrated quantum rotor model at commensurate filling in two dimensions. By developing a large- N method that is applicable to the model with frustration, we find the finite-size scaling properties in the spherical limit, from which the correlation length critical exponent ? = 1.0 and the dynamical critical exponent z = 1 are confirmed. A universal sheet resistance of R c / R 0 = 1.25(1) at the critical point, where R 0 is the quantum resistance, is obtained, which is consistent with the theoretical prediction.