Transport inefficiency in branched-out mesoscopic networks: An analog of the Braess paradox

TL;DR

This paper demonstrates that adding an extra branch to a mesoscopic quantum network can paradoxically decrease its conductance, revealing a quantum analog of the classical Braess paradox through simulations and experiments.

Contribution

It uncovers a quantum analog of the Braess paradox in mesoscopic networks, combining numerical simulations and scanning-probe experiments to show counter-intuitive transport behavior.

Findings

Adding a third branch reduces conductance in the network.

Scanning-probe measurements visualize the paradoxical conductance drop.

Numerical simulations confirm the counter-intuitive transport inefficiency.

Abstract

We present evidence for a counter-intuitive behavior of semiconductor mesoscopic networks that is the analog of the Braess paradox encountered in classical networks. A numerical simulation of quantum transport in a two-branch mesoscopic network reveals that adding a third branch can paradoxically induce transport inefficiency that manifests itself in a sizable conductance drop of the network. A scanning-probe experiment using a biased tip to modulate the transmission of one branch in the network reveals the occurrence of this paradox by mapping the conductance variation as a function of the tip voltage and position.