Special Quantum Matter Seminar

Screening is a ubiquitous process through which free and/or bound charges rearrange to reduce electric fields inside matter. This familiar behavior, in particular the sign of the effect, is a property of equilibrium matter. In this talk I will discuss how non-equilibrium driving can qualitatively transform the nature of screening in materials. In particular, I will show how driving inversion-symmetric graphene multilayers via incoherent photoexcitation or dc currents can transform screening into anti-screening -- the amplification of electric fields. Field amplification has no equilibrium analog, being forbidden by equilibrium stability criteria. Strikingly, under modest irradiation, photoexcitation can sustain broken-symmetry ferroelectric states with sizable hysteretic remnant polarizations. This work presents a new paradigm for achieving non-equilibrium broken symmetry phases, stabilized by nonlinear dynamical processes. This new regime opens a variety of intriguing questions about dynamics, interactions, and control of strongly correlated electronic phases.