Fluctuation-dissipation bounds in time-dependently driven conductors

We analyze the noise in a multiterminal multichannel conductor under arbitrary time-dependent driving and subject to—possibly large—static potential and temperature biases. We show that the full out-of-equilibrium zero-frequency noise is constrained by a fluctuation-dissipation bound. It consists of an upper bound expressed in terms of weighted current components of the separate Floquet bands arising from the time-dependent driving. In the limit of large static temperature bias, it has an intuitive interpretation in terms of the dissipated powers due to the static potential bias and due to the time-dependent driving. Furthermore, we show the existence of a second bound that relies on the specific shape of the electron distribution resulting from the driving, which can even be tighter than the fluctuation-dissipation bound in some parameter regimes. We show the implications of our bounds at the simple but experimentally relevant example of a two-terminal conductor in the presence of an ac bias.