Diode effect in Josephson junctions with a single magnetic atom

Area of Science:

• Condensed Matter Physics
• Quantum Electronics
• Materials Science

Background:

• Electronic devices exhibit directional current asymmetry, known as non-reciprocal charge transport, fundamental to diode functionality.
• The pursuit of low-dissipation electronics drives interest in superconducting diodes, with existing designs in non-centrosymmetric systems.
• Miniaturization of electronic components is a key goal in modern technology.

Purpose of the Study:

• To investigate the limits of miniaturization for superconducting diodes.
• To explore the creation and properties of atomic-scale Josephson junctions.
• To understand the mechanism behind non-reciprocal supercurrents at the atomic scale.

Main Methods:

• Fabrication of atomic-scale lead-lead (Pb-Pb) Josephson junctions using a scanning tunneling microscope.
• Introduction of single magnetic atoms into the junctions to induce asymmetry.
• Experimental characterization of junction behavior under varying bias directions.
• Theoretical modeling to elucidate the underlying physical mechanisms.

Main Results:

• Pristine atomic-scale Pb-Pb junctions showed hysteretic behavior but lacked directional asymmetry.
• Insertion of a single magnetic atom into the junction induced non-reciprocal supercurrents.
• The direction of non-reciprocity was found to be dependent on the specific magnetic atom introduced.
• Theoretical analysis identified electron-hole asymmetric Yu-Shiba-Rusinov states as the source of non-reciprocity.

Conclusions:

• Atomic-scale Josephson junctions can be engineered to function as diodes.
• Single-atom manipulation provides a novel method for tuning diode properties.
• The discovered mechanism offers new pathways for developing next-generation atomic-scale Josephson diodes.