Non-equilibrium universality in non-reciprocal coupled Ising models

While the physics of equilibrium phase transitions is well established, a full understanding of non-equilibrium phase transitions is still missing. On the other hand, non-equilibrium matter is increasingly realized in a variety of fields, from active matter to driven-dissipative quantum systems. In this talk, I will introduce a non-equilibrium variant of the Ashkin-Teller model in which two species of Ising spins experience a non-reciprocal coupling, explicitly breaking detailed balance and the equilibrium condition. Using Monte Carlo techniques, we show that this model possesses a multicritical point that exhibits exotic critical behavior, consistent with recent field-theoretical predictions. In particular, we show the extreme breakdown of the fluctuation-dissipation theorem, which is captured by the emergence of two distinct anomalous dimensions for the correlation and response functions with the former assuming a negative value, a feature with no counterpart in equilibrium.