Monochromatic electron emission from the macroscopic quantum state of a superconductor

K. Nagaoka, T. Yamashita, S. Uchiyama, M. Yamada, H. Fujii, C. Oshima

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The ground state of a superconductor is a macroscopic quantum state that can extend coherently over substantial distances. As a result, electrons tunnelling from two different points (separated by macroscopic length) on the surface of a superconductor remain coherent in phase and so are able to interfere: this property forms the basis of superconducting quantum interference devices (SQUIDs). Another characteristic of electrons tunnelling from a superconductor is that they are monochromatic, their energy being determined by the ground-state energy of the superconducting state. Monochromatic electrons have been observed tunnelling from a superconductor to a normal metal, and the resulting currents have been used to probe the dynamics of atoms and molecules at interfaces. Here we report the results of field-emission experiments that confirm the prediction that monochromatic electrons can similarly be emitted from a superconductor into vacuum. Monochromatic emissions of this type might find application as the sources in a range of electron-based spectroscopies.

Original languageEnglish
Pages (from-to)557-559
Number of pages3
Issue number6711
Publication statusPublished - 1998 Dec 10


ASJC Scopus subject areas

  • General

Cite this

Nagaoka, K., Yamashita, T., Uchiyama, S., Yamada, M., Fujii, H., & Oshima, C. (1998). Monochromatic electron emission from the macroscopic quantum state of a superconductor. Nature, 396(6711), 557-559.