Josephson ladders as a model system for 1D quantum phase transitions

Publication date: Available online 19 October 2018Source: Comptes Rendus PhysiqueAuthor(s): Matthew T. Bell, Benoît Douçot, Michael E. Gershenson, Lev B. Ioffe, Aleksandra PetkovićAbstractWe propose a novel platform for the study of quantum phase transitions in one dimension (1D QPT). The system consists of a specially designed chain of asymmetric SQUIDs; each SQUID contains several Josephson junctions with one junction shared between the nearest-neighbor SQUIDs. We develop the theoretical description of the low-energy part of the spectrum. In particular, we show that the system exhibits a quantum phase transition of Ising type. In the vicinity of the transition, the low-energy excitations of the system can be described by Majorana fermions. This allows us to compute the matrix elements of the physical perturbations in the low-energy sector. In the microwave experiments with this system, we explored the phase boundaries between the ordered and disordered phases and the critical behavior of the system's low-energy modes close to the transition. Due to the flexible chain design and control of the parameters of individual Josephson junctions, future experiments will be able to address the effects of non-integrability and disorder on the 1D QPT.RésuméNous proposons une nouvelle plateforme pour l'étude des transitions de phase quantiques en une dimension. Le système consiste en une chaîne de boucles de SQUID asymétriques spécialement configurées : chaque SQUID contient ...

Source: Comptes Rendus Physique - October 20, 2018 Category: Physics Source Type: research