Underlying connections among systems exhibiting directional-dependent superconducting transitions

Determine whether a common underlying connection exists among the directional-dependent superconducting transitions observed at EuO/KTaO3(111) interfaces with ferromagnetic EuO overlayers, LaAlO3/KTaO3 heterostructures, and infinite-layer nickelate superconducting thin films.

Background

This work demonstrates a directional-dependent Berezinskii–Kosterlitz–Thouless (BKT) transition at EuO/KTaO3(111) interfaces, with the highest T_BKT occurring when current flows along one [11̄2] axis, indicating spontaneous breaking of the expected threefold rotational symmetry. The effect is tightly linked to interfacial ferromagnetism and challenges the conventional single, global T_BKT picture for uniform 2D superconductors.

The authors note that related directional-dependent superconducting behavior has been reported recently in nonmagnetic LaAlO3/KTaO3 heterostructures and in infinite-layer nickelate thin films, though in those systems the anisotropy axes can be unrelated to crystallographic high-symmetry directions. Whether these phenomena share a common mechanism or organizing principle remains explicitly unresolved in the paper.

References

We have also noticed that evidence for directional-dependent superconducting transitions has recently been unveiled in nonmagnetic LAO/KTO heterostructures and infinite-layer nickelate thin films (yet both develop an arbitrary symmetry axis that is unrelated to any high-symmetry crystallographic directions); it is presently unknown whether there are underlying connections among all these cases.

— Directional-dependent Berezinskii-Kosterlitz-Thouless transition at EuO/KTaO$_3$(111) interfaces  (2604.00608 - Huang et al., 1 Apr 2026) in Main text, Discussion (final paragraphs)