Diode effect in Josephson junctions with a single magnetic atom

Abstract

Current flow in electronic devices can be asymmetric with bias direction, a phenomenon underlying the utility of diodes1 and known as non-reciprocal charge transport2. The promise of dissipationless electronics has recently stimulated the quest for superconducting diodes, and non-reciprocal superconducting devices have been realized in various non-centrosymmetric systems3–10. Here we investigate the ultimate limits of miniaturization by creating atomic-scale Pb–Pb Josephson junctions in a scanning tunnelling microscope. Pristine junctions stabilized by a single Pb atom exhibit hysteretic behaviour, confirming the high quality of the junctions, but no asymmetry between the bias directions. Non-reciprocal supercurrents emerge when inserting a single magnetic atom into the junction, with the preferred direction depending on the atomic species. Aided by theoretical modelling, we trace the non-reciprocity to quasiparticle currents flowing by means of electron–hole asymmetric Yu–Shiba–Rusinov states inside the superconducting energy gap and identify a new mechanism for diode behaviour in Josephson junctions. Our results open new avenues for creating atomic-scale Josephson diodes and tuning their properties through single-atom manipulation.

Phase diagrams of the diode effect in superconducting heterostructures

“…This supercurrent relation (17) is different from the conventional current formula, since it contains the covariant derivative  that takes into account the spin-momentum locking effect. Using the parameterized Green's functions the supercurrent densities in the F and S parts can be written as…”

“…Various systems that can behave as superconducting diodes have been recently theoretically proposed [4][5][6][7][8][9][10][11][12][13] and experimentally discovered [14][15][16][17][18][19][20][21][22][23]. The superconducting diode effect can be realized in two-dimensional (2D) superconducting systems if both inversion and time-reversal symmetries are broken [1].…”

Yu-Shiba-Rusinov states assisted by asymmetric Coulomb repulsion in a bipartite molecular device

“…The existence of highly anisotropic interactions, lasting up to very long distances are revealed in a hybrid system where two Cr adatoms adsorbs on Nb(110) surface, demonstrating the possibility of crossing a quantum phase transition (QPT) by tuning on the direction and interatomic distance between spins [24]. Coupled YSR states are found to be induced by intramolecular (Hund's-like) exchange interactions in a magnetic iron-porphyrin on Pb(111) [25], and superconducting diode effect by means of electron-hole asymmetric YSR states inside the energy gap are identified in Josephson junctions with a single magnetic atom [26].…”

Study on the Rectification of Ionic Diode Based on Cross-Linked Nanocellulose Bipolar Membranes

“…The junction between p-type and n-type semiconductors is a critical part of many electronic devices due to the asymmetric charge transport at the interface which only enables the transport of electrons/holes in one direction, known as rectification. , These electronics are the building blocks of modern digital technology due to their unique junction structure, such as diodes, photovoltaic cells, and transistors. − In biology, it is the ions in liquids rather than the electrons in solids that are the charge carrying particles used for different functions. For this reason, ions as signal carriers play essential roles in bioelectronic devices for applications such as ionic circuitry, sensory systems, and smart gating. , …”