Observation of two distinct pairs fluctuation lifetimes and supercurrents in the pseudogap regime of cuprate junctions

Abstract

Pairs fluctuation supercurrents and inverse lifetimes were measured on epitaxial c-axis junctions of the cuprates in the pseudogap regime, with a $PrB{a}_{2}C{u}_3{O}_{7-\delta }$ barrier sandwiched in between two $YB{a}_{2}C{u}_3{O}_{7-\delta }$ or doped $YB{a}_{2}C{u}_3{O}_y$ electrodes, with or without magnetic fields parallel to the a-b planes. All junctions had a ${\mathrm{T}}_{\mathrm{c}}(\mathrm{high})\approx 85-90$ K and a ${\mathrm{T}}_{\mathrm{c}}(\mathrm{low})\approx 50-55$ K electrodes, allowing us to study pairs fluctuation supercurrents and inverse life times in between these two temperatures. In junctions with a pseudogap electrode under zero field, an excesss current due to pair fluctuations was observed which persisted at temperatures above ${\mathrm{T}}_{\mathrm{c}}(\mathrm{low})$, in the pseudogap regime, and up to about ${\mathrm{T}}_{\mathrm{c}}(\mathrm{high})$. No such excess current was observed in junctions without a pseudo-gap in the electrode. The measured conductance spectra at temperatures above ${\mathrm{T}}_{\mathrm{c}}(\mathrm{low})$ were fitted using a modified fluctuations model by Scalapino [Phys. Rev. Lett. \textbf{24}, 1052(1970)] of a junction with a serial resistance. We found that in the pseudo-gap regime, the conductance vs voltage consists of a narrow peak sitting on top of a very broad peak. This yielded two distinct pairs fluctuation lifetimes in the pseudogap electrode which differ by an order of magnitude up to about ${\mathrm{T}}_{\mathrm{c}}(\mathrm{high})$. Under in-plane fields, these two lifetime values remain separated in two distinct groups, which varied with increasing field moderately. We also found that detection of Amperian pairing [Phys. Rev. X \textbf{4}, 031017 (2014)] in our cuprate junctions is not feasible, due to Josephson vortices penetration into the superconducting electrodes which drove the necessary field above the depairing field.

29 pages, 7+2 figures, Comments are welcome

References in corpus (4)

• Resonant X-ray Scattering Study of Charge Density Wave Correlations in YBa${}_2$Cu${}_3$O${}_{6+x}$
• X-ray diffraction observation of charge density wave order at zero magnetic field in ortho-II YBa${}_2$Cu${}_3$O${}_{6.54}$
• Parametric control of a superconducting flux qubit
• Flux-flow resistivity anisotropy in the instability regime in the a-b plane of epitaxial YBCO thin films

Cited by in corpus (4)

• Detection of collective modes in unconventional superconductors using tunneling spectroscopy
• Proximity effects and pair currents in cuprate junctions
• Precursory Cooper Flow in Ultralow-Temperature Superconductors
• Observation of Josephson-like tunneling junction characteristics and positive magnetoresistance in Oxygen deficient Nickelate films of $N{d}_{0.8}S{r}_{0.2}Ni{O}_{3-\delta }$