Dissipation-enhanced unidirectional transport in topological systems

Dissipation is a common occurrence in real-world systems and is generally considered detrimental to transport. In this paper, we examine the transport properties of a narrow quantum anomalous Hall system with dissipation applied on one edge. When the Fermi level resides within the hybridization gap, we find that, while transport is suppressed on one edge, it is significantly enhanced on the other. We reveal that the enhancement of the conductance on the other edge arises from dissipation-induced gap closure, which is deeply rooted in the point-gap topology of the system, resulting in a reduction of the decaying coefficient. When the dissipation is very large, we find that the low-energy physics is nearly indistinguishable from a narrower system, whose dissipation amplitude is inversely proportional to that of the original one. To get more physical intuition, we demonstrate that the low-energy physics can be well captured by a pair of coupled counterpropagating chiral edge states, one of which has a modified group velocity and an effective dissipation. We also briefly discuss the possible experimental realizations of this enhanced unidirectional transport.