Complex and tunable heating in conformal field theories with structured drives via classical ergodicity breaking

Abstract: Emission and absorption of energy are fundamental aspects of non-equilibrium dynamics. The heating induced by driving a many-body system is perhaps the most straightforward diagnostic of the process of equilibration, or the lack thereof. Gapless systems are particularly susceptible to drive-induced heating, and the capacity to control such heating is of experimental importance. Our study addresses this challenge in the framework of conformal field theory (CFT), for which we study families of structured drives up to the aperiodic Thue-Morse sequence. Concretely, we consider a class of spatially inhomogeneous Hamiltonians, where the operator evolution is governed by a non-linear classical dynamical system $\mathcal{K}$. The existence of invariant regions and fixed points of $\mathcal{K}$ leads to different levels of ergodicity breaking. Upon bridging the gap between this dynamical system and the driven CFT, we classify various dynamical phases of matter, including the heating and non-heating phases, as well as a prethermal phase with a controllably slow heating rate. We further generalize the discussion to $\eta-$random multipolar driving, characterized by $\eta-$th order multipolar correlation in time. A ``triply tunable'' parametric dependence of the prethermal lifetime arises as $K^{-2(\eta-\xi)}$, where $K$ quantifies the deviation from the preimages of the fixed points of $\mathcal{K}$, the multipolar order $\eta$, and the order of the preimages $\xi$. Upon sacrificing Hermiticity by considering SU(2) deformed CFTs, we find another non-heating phase with a non-zero measure, inaccessible via purely unitary CFTs. This is underpinned by an emergent compact subspace in the generic $\mathrm{SL}(2,\mathbb{C})$ group structure, which we also identify in the transfer matrix in non-Hermitian systems with binary disorder.