An incoherent superconducting nanowire phonon detector revealing the controversial gate-controlled supercurrent

Abstract

Superconductor nanodevices are widely applied in quantum computers and quantum detectors. Gate-controlled supercurrent (GCS) provides a potential platform for developing quantum systems, but the mechanism remains controversial. Recent reports suggest that there may be out-of-equilibrium phonons acting in GCS, but insightful investigations are lacking. Here, we report an incoherent superconducting nanowire phonon detector to convert the phase transitions induced by out-of-equilibrium phonons into electric pulse signals, enabling discrete-time measurements. The statistical properties of the gate-induced signals reveal the Poisson properties of phonon injection and the thermalization dynamics of hot electrons in the GCS on the α-Si substrate. These mechanisms are further evidenced by applying opposite gate voltages on two remote gates, in which only phonons play a role. The proposed detector not only is a candidate for constructing phonon-based solid quantum devices based on the GCS but also contributes to research on the out-of-equilibrium phenomena in superconducting nanodevices.