Superconducting-like heat current: Effective cancellation of current-dissipation trade off by quantum coherence*

Producing a large current typically requires large dissipation, as is the case in electric conduction, where Joule heating is proportional to the square of the current.
Quite recently, microscopic derivations and universal understanding of the trade-off relation between the current and dissipation based on stochastic thermodynamics have been put forward. Here we establish a universal framework clarifying how quantum coherence affects the current-dissipation trade-off relation:
proper use of coherence enhances the heat current without increasing dissipation, i.e. coherence can reduce friction. If the amount of coherence is large enough, this friction becomes virtually zero, realizing a superconducting-like ``dissipation-less'' heat current.
As an application, we construct a quantum heat engine that effectively attains the Carnot efficiency with finite power.
Since our framework clarifies a general relation among coherence, energy flow, and dissipation, it can be applied to many branches of science including quantum information theory, condensed matter physics, and biology.