A single atomic layer Pb/Si superconductor as a network of native Josephson junctions
Abstract
When the thickness of a superconductor is reduced approaching
the atomic limit, the modifications of its structural and electronic
properties, dimensionality and disorder strongly alter
superconductivity, generally leading to a metallic or an insulating
state. The surprising discovery of superconductivity in a material
consisting of a single atomic layer of Pb reconstructed √7x√3 on
Si(111) surface [1] raised an important question about its pure surface
origin, due to specific surface electronic states, as first suggested
in 1964 by V. L. Ginzburg [2]. Using well identified atomic scale
defects we probe the superconducting order in this material, from the
atomic to mesoscopic scales by means of STM/STS at ultra-low
temperature [3]. We found that the superconductivity is disrupted at
individual surface steps, which behave as native Josephson weak links
between superconducting terraces. In this atomically thin
superconducting network a peculiar vortex ordering occurs under
magnetic field. We anticipate that specific coherent transport
properties may be achieved, thus paving a new way of designing novel
atomic-scale quantum devices involving pre-patterned or vicinal
substrates, compatible with Si-technology [4].
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electrons at the surface levels. Zh. Exp. Teor. Fiz. 46, 397 (1964).
Sov. Phys. - JETP, 19, 269 (1964).
3. T. Cren et al. Phys. Rev. Lett., 107, 097202 (2011)
4. C. Brun et al. Nature Phys., submitted (2013)