Quantum Depletion of Superconductivity in 3D Diamond Nanowires

Superconducting nanowires underpin the development of a variety of highly advanced quantum devices such as single-photon detectors and quantum circuits. In 1D superconducting nanowires, topological fluctuations of the superconducting order parameter, known as phase slips, severely influence the electrical transport. In 3D systems, however, phase-slip events are generally considered to be insignificant. Here, details on the observation of a reentrant resistive state in 3D superconducting diamond nanowires (DNWs) are reported. This exotic resistive state alters the trend of the superconducting transition with an abrupt change of the temperature and magnetic-field coefficients of resistivity and the current coefficient of voltage. This reentrant resistive state is interpreted as being a result of quantum phase slips in the bamboo-like DNWs consisting of multiple sequential grain-boundary-grain junctions. The results provide the first evidence that quantum phase slips can also play a crucial role in determining the electrical transport properties of 3D superconducting nanowires.