Tip-induced superconducting and tunneling behavior in Nb/UTe₂ and PtIr/UTe₂ point contact junctions

Uranium ditelluride (UTe₂) is a novel superconducting material platform where a variety of exotic physics has been observed, such as chiral superconductivity, spin-triplet pairing, and unusual response to high magnetic fields [1–3]. Still, the nature of the superconducting order parameters and pairing symmetry remains uncertain, thus further requiring direct experimental evidence. Superconducting junction devices, such as Josephson junctions, can provide fruitful information on such properties in UTe₂. In this work, we investigated the electronic and superconducting properties of point contact junctions in UTe₂ single crystals using superconducting Nb and PtIr tips. Measurements were carried out down to ≈1.8 K, while the T_c of UTe₂ crystals was 1.6–2.0 K. Electrical measurements on Nb/UTe₂ point contact junctions showed a non-linear voltage–current behavior consistent with supercurrent flow, which was enhanced by uniaxial compression using Nb tips. Details about field response and pressure dependence of superconducting behavior in Nb/UTe₂ junctions will be discussed. We will also talk about the point-contact properties of UTe₂ crystals in PtIr/UTe₂ junctions.

[1] S. Ran et al. Nat. Phys. 15, 1250–1254 (2019).

[2] S. Ran et al. Science 365, 684–687 (2019).

[3] S. K. Lewin et al. Rep. Prog. Phys. 86, 114501 (2023).