Dissipative quantum phase transition in a head-to-tail atomic Josephson junction

We propose an alternative approach to observe a Schmid-Bulgadaev dissipative quantum phase transition (DQPT) with an atomic Bose Josephson junction (BJJ) in a head-to-tail configuration. The dissipation in the BJJ originates from the intrinsic momentum coupling between the coherent Josephson mode and the incoherent excitation modes, which leads to damped Langevin dynamics in the Josephson mode even without any synthetic dissipation. As a consequence of the intrinsic momentum coupling, we find the occurrence of the DQPT in the BJJ. This DQPT between a superconducting state and an insulating state was originally predicted in a resistively shunted Josephson junction (RSJJ) by Schmid and Bulgadaev 40 years ago, but the experimental verification has been yet challenging. In contrast to the RSJJ, we reveal that the DQPT in the head-to-tail BJJ is robust against nonperturbative effects suppressing the insulating state, and can be observed by controlling the interatomic interaction.