Coulomb drag in topological wires separated by an air gap

Electron-electron interactions between nanoscale wires lead to 1D Coulomb drag, which has significant ramifications on nanodevice performance beyond fundamental understanding of many body physics. Coulomb drag was theoretically discussed in quantum spin Hall (QSH) insulator holding 1D topological edges [1, 2, 3]，which however has not been realized experimentally. Here we report observation of 1D Coulomb drag between QSH edges separated by an air gap [4]. Negative drag signals are observed at low temperatures and show a nonmonotonic temperature dependence, suggesting that distinct drag mechanisms compete and essentially cancel out at higher temperatures. Nonmonotonic temperature dependence reveal the presence of the Dirac point in the 1D edges. Such observations present characteristic evidence of Coulomb drag between weakly disordered QSH edges. Our results demonstrate that the QSH effect can suppress impact of Coulomb interactions on nano-circuit performance, paving the way for topological integrated circuits.