Emergence of Chiral Order Driven by Quenched Disorder

Quenched disorder can destroy magnetic order, for example, when a random field is applied in a two-dimensional Ising model. Even when an order exists in the presence of quenched disorder, it is usually only the survival of the order of the clean model. We present here a surprising phenomenon where an order emerges, driven by quenched disorder. This order has nothing in common with the order present in the clean model. This type of order by disorder differs from the usual thermal or quantum one. The classical J_{1}-J_{3} Heisenberg model on the kagome lattice is studied by parallel tempering Monte Carlo simulations, with site dilution. After analyzing the effect of a few vacancies on the ground state, favoring noncoplanar configurations, we show the emergence of a low-temperature chiral phase and the progressive destruction of the collinear q=4 Potts order, the only order present in the absence of vacancies.