Hyperuniformity in Ashkin-Teller model.

We show that equilibrium systems inddimension that obey the inequalitydν>2,known as Harris criterion, exhibit suppressed energy fluctuation in their critical state. Ashkin-Teller model is an example ind = 2 where the correlation length exponentνvaries continuously with the inter-spin interaction strengthλand exceeds the valued2set by Harris criterion whenλis negative; there, the variance of the subsystem energy across a length scalelvaries asld-αwith hyperuniformity exponentα=2(1-ν-1).Point configurations constructed by assigning unity to the sites which has coarse-grained energy beyond a threshold value also exhibit suppressed number fluctuation and hyperuniformiyty with same exponentα.