Gate Tunable Dissipation and "Superconductor-Insulator" Transition in   Carbon Nanotube Josephson Transistors
  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. 
Gang Liu, Yong Zhang, Chun Ning Lau