Surface suppression of the superconducting energy gap and critical temperature in atomically thin NbSe<sub>2</sub>
ORAL
Abstract
The superconducting transition temperature of amorphous thin films often decreases dramatically as their thickness is reduced. This suppression can be attributed to either disorder-induced localization of Cooper pairs or generation of free vortices during Berezinskii-Kosterlitz-Thouless (BKT) transition. In the case of crystalline superconductors such as exfoliated NbSe2, superconductivity is preserved down to monolayer thickness, however, the transition temperature is also found to be suppressed.
Here we present measurements of both the superconducting energy gap Δ and critical temperature Tc in few-layer NbSe2, using planar-junction tunneling spectroscopy and lateral transport. We observe a fully developed gap that rapidly reduces for devices with the number of layers N ≥ 2 in the same way as their Tc. We attribute the observed behavior to inevitable depletion in the Cooper pair density in the immediate vicinity of the superconductor-vacuum interface. Our experimental data are in good agreement with the 1/N dependence of Δ and Tc predicted in this case. The involved spatial scale is only a few angstroms but cannot be ignored for atomically thin superconductors.
Here we present measurements of both the superconducting energy gap Δ and critical temperature Tc in few-layer NbSe2, using planar-junction tunneling spectroscopy and lateral transport. We observe a fully developed gap that rapidly reduces for devices with the number of layers N ≥ 2 in the same way as their Tc. We attribute the observed behavior to inevitable depletion in the Cooper pair density in the immediate vicinity of the superconductor-vacuum interface. Our experimental data are in good agreement with the 1/N dependence of Δ and Tc predicted in this case. The involved spatial scale is only a few angstroms but cannot be ignored for atomically thin superconductors.
*The University of Manchester (UK),
Engineering and Physical Sciences Research Council (UK),
European Research Council (EU)
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Presenters
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Ekaterina Khestanova
- School of Physics and Astronomy, University of Manchester