Parity effect and single-electron injection for Josephson-junction chains deep in the insulating state

Abstract

We have made a systematic investigation of charge transport in 1D chains of Josephson junctions where the characteristic Josephson energy is much less than the single-island Cooper-pair charging energy, $E_{\mathrm{J}}\ll E_{CP}$. Such chains are deep in the insulating state, where superconducting phase coherence across the chain is absent, and a voltage threshold for conduction is observed at the lowest temperatures. We find that Cooper-pair tunneling in such chains is completely suppressed. Instead, charge transport is dominated by tunneling of single electrons, which is very sensitive to the presence of BCS quasiparticles on the superconducting islands of the chain. Consequently we observe a strong parity effect, where the threshold voltage vanishes sharply at a characteristic parity temperature $T^{\ast }$, which is significantly lower than the the critical temperature, $T_c$. A measurable and thermally-activated zero-bias conductance appears above $T^{\ast }$, with an activation energy equal to the superconducting gap, confirming the role of thermally-excited quasiparticles. Conduction below $T^{\ast }$ and above the voltage threshold occurs via injection of single electrons/holes into the Cooper-pair insulator, forming a non-equilibrium steady state with a significantly enhanced effective temperature. Our results explicitly show that single-electron transport dominates deep in the insulating state of Josephson-junction arrays. This conduction process has mostly been ignored in previous studies of both superconducting junction arrays and granular superconducting films below the superconductor-insulator quantum phase transition.

8 pages, 6 figures

References in corpus (9)

• Measurement and Control of Quasiparticle Dynamics in a Superconducting Qubit
• Implementation of low-loss superinductances for quantum circuits
• Collective transport in the insulating state of Josephson junction arrays
• Quantum Phase Slips in one-dimensional Josephson Junction Chains
• Tunneling and Relaxation of Single Quasiparticles in a Normal-Superconductor-Normal Single Electron Transistor
• Thermally activated conductance in arrays of small Josephson junctions
• The parity effect in Josephson junction arrays
• Correlated transport through junction arrays in the small Josephson energy limit: incoherent Cooper-pairs and hot electrons
• Crossover from time-correlated single-electron tunneling to that of Cooper pairs

Cited by in corpus (10)

• Insulating Josephson-junction chains as pinned Luttinger liquids
• Keldysh meets Lindblad: Correlated Gain and Loss in Higher-Order Perturbation Theory
• Dephasing-assisted Gain and Loss in Mesoscopic Quantum Systems
• Second-harmonic generation enhancement in monolayer transition-metal dichalcogenides by an epsilon-near-zero substrate
• Tunable ohmic environment using Josephson junction chains
• Detecting parity effect in a superconducting device in the presence of parity switches
• The influence of pinholes and weak-points in aluminium-oxide Josephson junctions
• Cooper-Pair Tunneling in Small Josephson Junction Arrays under Radio-Frequency Irradiation
• Linear response theory of Josephson junction arrays in a microwave cavity
• Renormalization of Electromagnetic Quantities in Small Josephson Junctions