Absence versus Presence of Dissipative Quantum Phase Transition in Josephson Junctions

Area of Science:

• Quantum physics
• Condensed matter physics

Background:

• Dissipative quantum phase transitions are theoretically predicted in Josephson junctions coupled to resistors.
• Experimental evidence remains scarce, leading to ongoing debate.

Purpose of the Study:

• To investigate the behavior of Josephson junctions coupled to resistors using nonperturbative methods.
• To challenge conventional understanding of dissipative quantum phase transitions.

Main Methods:

• Numerical and analytical nonperturbative renormalization group analyses were employed.
• The study focused on renormalization group flows in nonperturbative regimes.

Main Results:

• Perturbative arguments were found to be flawed, and the transition does not always occur at the quantum resistance R_{Q}=h/(4e^{2}).
• Nonmonotonic renormalization of charging energy was observed, leading to a suppressed insulator phase in the Cooper pair box regime.
• The transmon regime was found to be always superconducting.

Conclusions:

• A previously overlooked term explains the failure of conventional theories.
• Predictions are testable in experiments with high-impedance superconducting waveguides.
• This work offers a resolution to the controversy surrounding dissipative quantum phase transitions in resistively shunted Josephson junctions.