Fig. 3. Algebraic scaling of uniform magnetic susceptibility.

At high temperature T ≳ 4 K, χ(h, T) remains independent of h for small fields, which indicates an exponent of α = 0 in χ(h, T) ~ h^−α(T), whereas for 1 K ≲ T ≲ 4 K (shaded regime), χ(h, T) exhibits an universal scaling vs. h with α ≠ 0. For temperatures below $T_{\mathrm{l}}^{*}~1$ K, the susceptibility ceases to increase as the system orders into the clock phase. In the inset, χ(h, T) vs. h curves are presented in the log–log plot, where the algebraic scaling manifests itself in the KT phase (and in the clock phase due to the saturation). The fitted η values decrease from 2/9 gradually to  ~0.15, the deviation of the latter from the expectation of 1∕9 is ascribed to limited lattice size (L = 12 torus) adopted in the QMC calculations.