Gate Tunable Dissipation and "Superconductor-Insulator" Transition in Carbon Nanotube Josephson Transistors

TL;DR

This study explores how dissipation and quantum coherence in carbon nanotube Josephson transistors can be controlled via gate voltage, revealing a tunable transition between superconducting and insulating states linked to resistance.

Contribution

It demonstrates gate-tunable dissipation and a superconductor-insulator transition in carbon nanotube Josephson transistors, highlighting the role of normal resistance in quantum state control.

Findings

Voltage-current hysteresis correlates with normal resistance.

Gate tuning induces a transition from superconducting-like to insulating-like states.

Critical resistance for transition is approximately 8-20 kohm.

Abstract

Dissipation is ubiquitous in quantum systems, and its interplay with fluctuations is critical to maintaining quantum coherence. We experimentally investigate the dissipation dynamics in single-walled carbon nanotubes coupled to superconductors. The voltage-current characteristics display gate-tunable hysteresis, with sizes that perfectly correlate with the normal state resistance RN, indicating the junction undergoes a periodic modulation between underdamped and overdamped regimes. Surprisingly, when a device's Fermi-level is tuned through a local conductance minimum, we observe a gate-controlled transition from superconducting-like to insulating-like states, with a "critical" R_N value of about 8-20 kohm.