Electron irradiation reveals robust fully gapped superconductivity in LaNiGa$_{2}$

S. Ghimire; K. R. Joshi; E. H. Krenkel; M. A. Tanatar; Yunshu Shi; M. Konczykowski; R. Grasset; V. Taufour; P. P. Orth; M. S. Scheurer; R. Prozorov

doi:10.1103/physrevb.109.024515

arXiv · 2311.12222

Electron irradiation reveals robust fully gapped superconductivity in LaNiGa$_{2}$

S. Ghimire·K. R. Joshi·E. H. Krenkel·M. A. Tanatar·Yunshu Shi·M. Konczykowski·R. Grasset·V. Taufour·P. P. Orth·M. S. Scheurer·R. Prozorov

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Abstract

The effects of 2.5 MeV electron irradiation were studied in the superconducting phase of single crystals of LaNiGa$_2$, using measurements of electrical transport and radio-frequency magnetic susceptibility. The London penetration depth is found to vary exponentially with temperature, suggesting a fully gapped Fermi surface. The inferred superfluid density is close to that of a single-gap weak-coupling isotropic $s-$wave superconductor. Superconductivity is extremely robust against nonmagnetic point-like disorder induced by electron irradiation. Our results place strong constraints on the previously proposed triplet pairing state by requiring fine-tuned impurity scattering amplitudes and are most naturally explained by a sign-preserving, weak-coupling, and approximately momentum independent singlet superconducting state in LaNiGa$_2$, which does not break time-reversal symmetry. We discuss how our findings could be reconciled with previous measurements indicating magnetic moments in the superconducting phase.

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S. Ghimire, K. R. Joshi, E. H. Krenkel, M. A. Tanatar, Yunshu Shi, M. Konczykowski, R. Grasset, V. Taufour, P. P. Orth, M. S. Scheurer, R. Prozorov. 2023-11-20. Electron irradiation reveals robust fully gapped superconductivity in LaNiGa$_{2}$. https://doi.org/10.1103/physrevb.109.024515

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