Strain-gradient driven superconductivity in GdAuGe hexagonal Heusler membranes*

Recent experiments and theory suggest that the rare earth half-Heusler compounds RPtBi [1] and their hexagonal cousins such as SrPtAs [2] are spin triplet superconductors. However, the low T_C of 0.77 K for YPtBi [1] prohibits their study via spectroscopic probes that would help to understand the pairing, e.g., STM and ARPES. Here, starting from single crystalline membranes of a similar hexagonal Heusler GdAuGe, we found that large strain gradient induces superconductivity in this material when rippled. Unstrained GdAuGe is antiferromagnetic below ~17 K and remains antiferromagnetic with homogeneous strain. When subjected to extreme strain gradients, GdAuGe shows superconductivity below∼4 K, as detected via Meissner effect, and a critical field phase diagram congruent with a type II superconductor. The presence of coexisting antiferromagnetic ordering is consistent with the superconductivity in non-centrosymmetric half-Heuslers YPtBi [1] and HoPdBi [3] and the Fe based superconductors [4] where the ordered state destabilizes into a configuration that support spin fluctuations and leads to cooper pairing. Our results emphasize the potential of strain gradient engineering in membranes of quantum material in accessing new phases which are otherwise inaccessible in the material.

1.T. Takenaka et al, Science Advances, 7, 12, (2021).

2.M. H. Fischer et al, Phys. Rev. B 89,020509(R) (2014)

3.A M Nikitin et al, 2015 J. Phys.: Condens. Matter 27

4.C. Liu et al, Phys. Rev. Lett. 128, 137003 (2022).