Hybrid single-electron transistor as a source of quantized electric current

The basis of synchronous manipulation of individual electrons in solid-state devices was laid by the rise of single electronics about two decades ago(1-3). Ultrasmall structures in a low-temperature environment form an ideal domain for addressing electrons one by one. In the so-called metrological triangle, voltage from the Josephson effect and resistance from the quantum Hall effect would be tested against current via Ohm's law for a consistency check of the fundamental constants of nature, h and e (ref. 4). Several attempts to create a metrological current source that would comply with the demanding criteria of extreme accuracy, high yield and implementation with not too many control parameters have been reported(5-11). Here, we propose and prove the unexpected concept of a hybrid normal-metal-superconductor turnstile in the form of a one-island single-electron transistor with one gate, which demonstrates robust current plateaux at multiple levels of ef at frequency f.