Quantum Phase Slips in one-dimensional Josephson Junction Chains

TL;DR

This paper investigates quantum phase-slip phenomena in long one-dimensional Josephson junction chains with tunable coupling, revealing how QPS influence resistance and current-voltage behavior, especially near the quantum resistance threshold.

Contribution

It provides experimental evidence of quantum phase-slip effects in long Josephson junction chains with a weak link, demonstrating the exponential dependence of resistance on coupling and the transition to Coulomb blockade.

Findings

Finite zero-bias resistance explained by QPS with exponential dependence on √(E_J/E_C)

Observation of Coulomb blockade remnants in IVC when resistance exceeds R_Q

Identification of coherent QPS enhancement at the weak link

Abstract

We have studied quantum phase-slip (QPS) phenomena in long one-dimensional Josephson junction series arrays with tunable Josephson coupling. These chains were fabricated with as many as 2888 junctions, where one sample had a tunable weak link in the middle. Measurements were made of the zero-bias resistance, $R_0$, as well as current-voltage characteristics (IVC). The finite $R_0$ is explained by QPS and shows an exponential dependence on $\sqrt{E_J/E_C}$ with a distinct change in the exponent at $R_0=R_Q=h/4e^2$. When $R_0 > R_Q$ the IVC clearly shows a remnant of the Coulomb blockade, which evolves to a zero-current state with a sharp critical voltage as $E_J$ is tuned to a smaller value. The zero-current state below the critical voltage is due to coherent QPS and we show that these are enhanced at the central weak link. Above the critical voltage a negative differential resistance is observed which nearly restores the zero-current state.