Abstract
Although giant proximity effect (GPE) can shed important information on understanding superconducting pairing mechanisms and superconducting electronics, reports on the GPE are few because the fabrication of the junctions with GPE is technologically difficult. Here, we report a GPE in the single-crystalline MgB2 bilayers (S′/S), where the S′ is the damaged MgB2 layer by cobalt (Co)-ion irradiation and the S is the undamaged MgB2 layer. Superconducting properties of the S′ is remarkably degraded by the irradiation, whereas those of the S is uninfluenced by the irradiation. The degraded superconductivity in the S′ is fully recovered by increasing the thickness of undamaged MgB2 layer S despite almost ten times larger thickness ~ 95 nm of S′ than the superconducting coherence length ξab(0) ~ 8.5 nm of the S, indicating a presence of GPE in the S′/S MgB2 bilayers. A diffusion of electrons in the S′ into the S can reduce a pair breaking scattering in the S′, and the similar electronic structures of S′ and S layers and a finite attractive electron-electron interaction in the S′ are thought to be origins of unpredicted GPE between the same superconducting materials. Both upper critical field (μ0Hc2) and in-field critical current density (Jc) of S′/S bilayers show a significant enhancement, representing a strong correlation between S′ and S. These discoveries provide the blue print to the design of the superconducting multilayers for fundamental researches on the mechanism of the GPE as well as their technological applications.
Highlights
The superconducting proximity effect (PE), a leak of Cooper pairs from a superconductor (S) into a normal metal (N) when they are in contact with each other, is a fascinating phenomenon that is critical to the design of superconducting electronic devices, such as superconducting quantum interface device (SQUID) and quantum information device[1,2,3,4]
Unpredicted large PE was observed when superconductor S1 is connected with another superconductor S2 instead of normal metal, which is known as the giant proximity effect (GPE)[11,12,13,14,15,16,17]
Upper critical field (μ0Hc2) of the single-crystalline MgB2 bilayers (S′/S) bilayers has two times larger value than that of the pristine films, and field performance of critical current density (Jc) of the bilayers is superior to that of the pristine MgB2 films. These results demonstrate that the existence of giant proximity effect in the S′/S MgB2 bilayers provides a blue print to fabricate superconducting MgB2 multilayers for their fundamental researches as well as technological applications
Summary
The superconducting proximity effect (PE), a leak of Cooper pairs from a superconductor (S) into a normal metal (N) when they are in contact with each other, is a fascinating phenomenon that is critical to the design of superconducting electronic devices, such as superconducting quantum interface device (SQUID) and quantum information device[1,2,3,4]. Superconducting coherence length (ξ) and electronic mean free path (l) in the normal metal are important parameters to determine the leaking distance of Cooper pairs in S/N junctions, which have been intensively studied and well understood based on conventional theories[2,3,5,6,7,8,9,10]. The Cooper-pair leaking distance in S1/S2 junctions is almost ten times larger than the coherence length ξ, and Josephson critical current could be much improved in the superconducting multilayers composed of the optimally doped and under doped high-Tc cuprates, such as LSCO (La2-xSrxCuO4)/LCO (La2CuO4+δ)/LSCO trilayer[13,14,15]. Conventional superconductor MgB2 with relatively high Tc of 40 K is a good candidate for GPE realization via the ion irradiation technique because of its large superconducting coherence length, metallicity, and large superconducting energy gap[25,26]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
