Abnormal supercurrent diode effect in Josephson junctions of Au(111)/Nb with epitaxial tellurium barrier*

Supercurrent diode effect has recently gained attentions as a non-reciprocal phenomenon in

superconductors with both broken inversion symmetry and broken time-reversal symmetry.

When an external magnetic field is applied perpendicular to the direction of the supercurrent,

mechanism such as finite Cooper pair momentum would lead to an odd-in-field diode effect. In

this talk, we will present our approach to engineer the broken symmetries in fabricated

Josephson junctions made on top of epitaxially grown Au(111)/Nb layers that host strong spin-

orbit coupling at the surface. We adopt a special tunnel barrier material, i.e. the epitaxially

grown tellurium in the trigonal phase, in an asymmetric Josephson junction made between

Au(111)/Nb and aluminum, in which quasiparticles at the junction’s interface may experience a

rich range of interactions. We will first demonstrate robust Josephson supercurrent diode effect

in such junctions with a large diode efficiency. We will further show our detailed measurements

regarding an abnormal field dependence of the diode effect, and open discussions to potential

mechanism contributing to the abnormal supercurrent diode effect.