Attractive Coulomb interactions in a triple quantum dot

TL;DR

This study demonstrates how Coulomb interactions in a triple quantum dot can induce electron pairing mediated by the third dot, revealing complex electron correlation effects with potential for novel functionalities.

Contribution

It experimentally shows Coulomb-mediated electron pairing in a TQD and links degeneracy conditions to transport behavior, advancing understanding of correlated electron systems.

Findings

Electron pairing is mediated by the third dot in a TQD.

Degeneracy in charge configurations is achieved through Coulomb coupling.

Transport spectroscopy reveals nontrivial electron transport behavior.

Abstract

Electron pairing due to a repulsive Coulomb interaction in a triple quantum dot (TQD) is experimentally studied. It is found that electron pairing in two dots of a TQD is mediated by the third dot, when the third dot strongly couples with the other two via Coulomb repulsion so that the TQD is in the twofold degenerate ground states of (1, 0, 0) and (0, 1, 1) charge configurations. Using the transport spectroscopy that monitors electron transport through each individual dot of a TQD, we analyze how to achieve the degeneracy in experiments, how the degeneracy is related to electron pairing, and the resulting nontrivial behavior of electron transport. Our findings may be used to design a system with nontrivial electron correlations and functionalities.