Coulomb blockade and Bloch oscillations in superconducting Ti nanowires

TL;DR

This paper provides experimental evidence that quantum phase slips in superconducting Ti nanowires cause Coulomb blockade and Bloch oscillations, demonstrating quantum duality between Josephson junctions and nanowires.

Contribution

It experimentally demonstrates Coulomb blockade and Bloch oscillations in superconducting Ti nanowires due to quantum phase slips, highlighting the quantum duality with Josephson junctions.

Findings

Quantum phase slips cause Coulomb blockade in Ti nanowires.

RF radiation induces synchronized Bloch oscillations.

Observation of quantized current steps in I-V characteristics.

Abstract

Quantum fluctuations in quasi-one-dimensional superconducting channels leading to spontaneous changes of the phase of the order parameter by $2\pi$, alternatively called quantum phase slips (QPS), manifest themselves as the finite resistance well below the critical temperature of thin superconducting nanowires and the suppression of persistent currents in tiny superconducting nanorings. Here we report the experimental evidence that in a current-biased superconducting nanowire the same QPS process is responsible for the insulating state -- the Coulomb blockade. When exposed to RF radiation, the internal Bloch oscillations can be synchronized with the external RF drive leading to formation of quantized current steps on the I-V characteristic. The effects originate from the fundamental quantum duality of a Josephson junction and a superconducting nanowire governed by QPS -- the QPS junction (QPSJ).