Scientists directly observe heavy-fermion state at atom-thin layer and metal interface

A University of Osaka-led team grew a one-atom-thick YbCu₂ layer on a copper crystal and used synchrotron light to directly observe two heavy-fermion states — one confined to the 2D layer and one extending into the 3D copper substrate. The finding points to new ways of engineering quantum materials and unconventional superconductivity.

• One-atom-thick YbCu₂ layer grown on a Cu(111) copper crystal
• Two distinct heavy-fermion states found: in the 2D layer and the 3D substrate
• The second state arose from hybridization of ytterbium 4f and conduction electrons
• Results published in Communications Materials on October 6, 2026