JERUSALEM, March 31 (Xinhua) -- A Hebrew University of Jerusalem (HU)-led study has identified unusual superconducting behavior in ultra-thin material samples, challenging prior assumptions about how these materials function at microscopic scales, the university said on Monday.
Superconductors, which conduct electricity without energy loss, are widely used in technologies such as medical imaging and quantum computing.
While their properties typically shift gradually as they are made thinner, the study found that below a critical thickness -- just a few atomic layers -- electric current flows predominantly along their top and bottom surfaces rather than through the entire material.
Published in Nature Communications, the research focused on niobium diselenide (NbSe2), a layered superconducting material that can be precisely thinned to atomic-level precision. Using specialized magnetic imaging, the team measured how the material's ability to repel magnetic fields, quantified by a property called Pearl length, changed with thickness.
In samples thicker than 10 atomic layers, Pearl length correlated with thickness as expected. However, in films of three to six layers (two-four nanometers thick), Pearl length surged dramatically and became independent of thickness, a result that contradicts traditional models of superconductivity.
"This suggests superconductivity in extremely thin materials is dominated by surface effects rather than bulk properties," researchers noted, adding that the findings underscore the need to revisit theoretical frameworks for nanoscale superconductors. ■
