Gapless materials, which are inert gap materials in contact with superconductor electrons, obtain neighboring induced superconductivity in the region near the interface. Many proposals are based on adding electron pairing to the original non superconducting system and predicting material phases, including topology, odd frequency, node node node node or Fulde Ferrell Larkin Ovchinnikov superconductivity.

Today, Lucas Schneider et al. from the University ä t Hamburg in Germany published an article on Nature. In the quantum corral of a superconducting substrate, the surface state is bound only to a single spin degenerate quantum level, and based on scanning tunneling microscopy, the smallest example of proximity effect is constructed atomically.

Based on adjusting the size of the quantum fence, whenever the eigenmode of the quantum fence approaches Fermi energy, a pair of particle hole symmetric states will enter the energy gap of the superconductor. Research has determined that these are spin degenerate Andreev bound states (predicted theoretically by Machida and Shibata 50 years ago), which have not yet been detected by tunnel spectroscopy, but have recently been proven to be related to Transmon quantum bit devices.

Further research has found that the observed anti crossing anticrossings of the in gap states are a measure of neighboring induced pairing in the eigenmodes of quantum fences. This study has a direct impact on explaining the energy gap states induced by impurities in superconductors, confirming the concept of inducing superconductivity to surface states, and further paving the way for superconducting artificial lattices.

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