Low temperature two STM tip tunneling measurements of a floating chemical potential Pb(111) surface
CEMES, Université de Toulouse, CNRS, 29 Rue J. Marvig, BP 94347, 31055 Toulouse Cedex, France
2 International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki, Tsukuba, Ibaraki 305-0044, Japan
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Received in final form: 4 September 2019
Accepted: 1 October 2019
Published online: 8 November 2019
On a Pb(111) superconducting surface, low temperature dI/dV tunnelling spectra are recorded between two scanning tunnelling microscopes (STM) metallic tips with the Pb(111) sample metallic support non-grounded. The tunnelling current intensity I passing between the 2 tips through the sample is controlled by changing one or both STM vacuum tunnelling junction resistances. The chemical potential of this floating Pb(111) surface depends on the normalized ratio between those two quantum resistances. When ungrounded, the Pb(111) sample chemical potential balances between those of the 2 STM tips while tuning their respective tip end atomic apex to Pb(111) surface distances with a picometer precision without any physical contact between the STM tips and the surface.
© W.-H. Soe et al., EDP Sciences, 2019
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