Approaching Two-Dimensional Superconductivity in Ultrathin DyBa_{2}Cu_{3}O_{7-δ}.

R D Dawson,D Putzky,G Logvenov,K S Rabinovich,A V Boris,G Christiani,B Keimer

doi:10.1103/physrevlett.125.237001

R D Dawson, D Putzky + Show 5 more

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https://doi.org/10.1103/physrevlett.125.237001

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Abstract

The temperature dependence of the superfluid density ρ_{s}(T) has been measured for a series of ultrathin MBE-grown DyBa_{2}Cu_{3}O_{7-δ} superconducting (SC) films by submillimeter wave interferometry combined with time-domain terahertz spectroscopy and IR ellipsometry. We find that all films 10u.c. and thicker show the same universal temperature dependence of ρ_{s}(T), which follows the critical behavior characteristic of single crystal YBa_{2}Cu_{3}O_{7-δ} as T approaches T_{c}. In 7u.c. thick films, ρ_{s}(T) declines steeply upon approaching T_{c}, as expected for the Berezinskii-Kosterlitz-Thouless vortex unbinding transition. Our analysis provides evidence for a sharply defined 4u.c. non-SC interfacial layer, leaving a quasi-2D SC layer on top. We propose that the SC state in this interfacial layer is suppressed by competing (possibly charge) order.

Highlights

The temperature dependence of the superfluid density ρsðTÞ has been measured for a series of ultrathin molecular beam epitaxy (MBE)-grown DyBa2Cu3O7-δ superconducting (SC) films by submillimeter wave interferometry combined with time-domain terahertz spectroscopy and IR ellipsometry
The commonality of the layered CuO2 plane structure to all families of copper oxide high-Tc superconductors (HTSCs) implies that understanding the effect of reduced dimensionality on superconductivity in the cuprates is key to elucidating the mechanism of HTSC
In this Letter, we report the temperature and thickness dependence of ρs in a series of near-optimally doped DyBCO ultrathin films grown by molecular beam epitaxy (MBE)

Summary

Published by the American Physical Society

(LaAlO3Þ0.3ðSr2AlTaO6Þ0.7 (LSAT) substrates of dimensions 10 × 10 mm by ozone-assisted atomic-layer-bylayer oxide MBE, and the high crystal structure quality of the films was confirmed by x-ray diffraction and transmission electron microscopy measurements, as reported elsewhere [16]. The results reported here are primarily based on measurements of the complex transmission obtained with a tabletop quasioptical submillimeter-wave Mach-Zehnder interferometer. These measurements were supplemented by broadband measurements of the complex dielectric function via combined time-domain terahertz spectroscopy and far-infrared-to-UV ellipsometry [17]

The real part of the conductivity shows a maximum below

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