Floquet Scattering Matrix Theory of Heat Fluctuations in Dynamical Quantum Conductors

I present the Floquet scattering matrix theory of low-frequency heat fluctuations in driven quantum-coherent conductors in the linear response regime and beyond. The Floquet theory elucidates the use of the Callen-Welton fluctuation-dissipation theorem for a description of heat fluctuations in a multiterminal case. The intrinsic fluctuations of energy of dynamically excited electrons are identified as the fundamental source of heat noise not revealed by the electrical noise. The role of backscattering in the increase of heat noise above the level defined by the Callen-Welton theorem is highlighted. The exception is the case when a conductor is driven by a Lorentzian voltage pulse with quantized flux. The heat noise in this case falls down to the level pertaining to a linear response regime.

Figure 1

A sketch of a ballistic conductor (or a Hall bar with chiral edge states) interrupted by a quantum point contact (QPC) shown as a constriction. A voltage bias $V$ across a QPC induces an electron flux, shown by arrows, transmitted and reflected at a QPC.