Masuki Kanta, Sudo Hiroyuki, Oshikawa Masaki, Ashida Yuto
Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Phys Rev Lett. 2022 Aug 19;129(8):087001. doi: 10.1103/PhysRevLett.129.087001.
Dissipative quantum phase transition has been widely believed to occur in a Josephson junction coupled to a resistor despite a lack of concrete experimental evidence. Here, on the basis of both numerical and analytical nonperturbative renormalization group analyses, we reveal breakdown of previous perturbative arguments and defy the common wisdom that the transition always occurs at the quantum resistance R_{Q}=h/(4e^{2}). We find that renormalization group flows in nonperturbative regimes induce nonmonotonic renormalization of the charging energy and lead to a qualitatively different phase diagram, where the insulator phase is strongly suppressed to the deep charge regime (Cooper pair box), while the system is always superconducting in the transmon regime. We identify a previously overlooked dangerously irrelevant term as an origin of the failure of conventional understandings. Our predictions can be tested in recent experiments realizing high-impedance long superconducting waveguides and would provide a solution to the long-standing controversy about the fate of dissipative quantum phase transition in the resistively shunted Josephson junction.
尽管缺乏具体的实验证据，但人们普遍认为耗散量子相变会发生在与电阻器耦合的约瑟夫森结中。在此，基于数值和解析非微扰重整化群分析，我们揭示了先前微扰论证的失效，并挑战了那种认为相变总是发生在量子电阻(R_{Q}=h/(4e^{2}))处的普遍观点。我们发现，非微扰区域中的重整化群流会导致充电能量的非单调重整化，并导致一个性质不同的相图，其中绝缘相被强烈抑制到深电荷区域（库珀对盒），而在跨导量子比特区域系统总是超导的。我们确定了一个先前被忽视的危险无关项，它是传统理解失败的根源。我们的预测可以在最近实现高阻抗长超导波导的实验中得到验证，并将为关于电阻分流约瑟夫森结中耗散量子相变命运的长期争议提供一个解决方案。
