Excitonic Josephson effect induced by interlayer tunneling current: robust evidence for exciton condensation

Abstract

Josephson effect ever stimulated a lot of activity in quantum Hall bilayer exciton condensates since the observation of Josephson-like tunneling and recently even receives great attention in optically excited exciton-polariton condensates. The intense interest is originated from that Josephson effect can be regarded as one of the most striking manifestations of exciton or exciton-polariton condensates. Following the proposal by Park and Das Sarma [Phys. Rev. B 74, 035338 ( 2006)], we study the excitonic Josephson junction with relative phases induced by interlayer tunneling currents. Our results indicate the novel coupling of edge tunneling currents [Phys. Rev. Lett. 109, 156802 (2012)] can be explained by tunneling-current induced Josephson effect and is a very robust evidence for exciton condensation. Also, we furthermore suggest to detect Josephson current by measuring induced magnetic field of a ring-shape excitonic Josephson junction.

Role of the compensating current in the weak Josphson coupling regime: An extended study on excitonic Josephson junctions

“…1(c). We find the length reduction effect is revealed by the crossover of the B J versus (J tR − J tL ) curve into the short junction regime 50 , becoming a linear one, with increasing the compensating current. The induced magnetic field is estimated at ∼ 100pT that is large enough to be detected by the scanning superconducting interference device (SQUID).…”

“…1(a). The tunneling currents (J tL ,J tR ) twist the condensate phases of two edges so as to create the relative phases between three condensates: EC1, EC2, and EC3 50 . Such structure is regarded as two condensates (EC1 and EC3) sandwiched by a superfluid barrier (EC3), which is a type of excitonic Josephson junctions 51 .…”

“…Such structure is regarded as two condensates (EC1 and EC3) sandwiched by a superfluid barrier (EC3), which is a type of excitonic Josephson junctions 51 . Our another work 50 has explored this setup but focuses on the short junction whose junction length L is smaller than Josephson length λ 52 . Its results demonstrated that the exotic coupling phenomenon of edge tunneling currents observed by Huang et al 49 is originated from excitonic Josephson effect and Huang's experiment may be by far the most robust evidence for quantum Hall bilayer exciton condensation, making a big contribution to the exact identification of exciton condensation, which has long been an important issue.…”

“…Its results demonstrated that the exotic coupling phenomenon of edge tunneling currents observed by Huang et al 49 is originated from excitonic Josephson effect and Huang's experiment may be by far the most robust evidence for quantum Hall bilayer exciton condensation, making a big contribution to the exact identification of exciton condensation, which has long been an important issue. In particular, the excitonic Josephson effect induced by tunneling current display new physics that are not seen in conventional superconductors 51 : coexistence of anti-parallel supercurrents and controllability by switching tunneling-current polarity 50 .…”

“…1(b)]. It is therefore highly desirable that the long junction can display entirely different properties from the short junction in which two edges are strongly Josephson coupled 50 .…”