Type-I superconductivity in the Weyl semimetal TaGe2 with chiral structure

Abstract

Nonmagnetic chiral crystals host Kramers-Weyl fermions at time-inversion invariant momenta and can exhibit a topological nontrivial Fermi surface. Exploring topological superconductivity in chiral materials is thus an area of active research. In this study, we have successfully grown high-quality single crystals of TaGe2 which adopt a chiral hexagonal lattice structure. We conducted comprehensive experimental measurements on superconductivity, complemented by theoretical calculations. Magnetic property, electrical resistivity, and heat capacity data indicate that TaGe2 undergoes a type-I superconducting transition at 1.9 K. Further analysis of low-temperature heat capacity data suggest that TaGe2 is a weakly coupled single-band BCS superconductor. We constructed a phase diagram of critical field obtained by heat capacity and electrical resistivity measurements. Surface superconductivity was observed in this type-I superconductor with a κ value of 0.074, and the ratio of surface critical field (μ0Hs) to the bulk critical field (μ0Hc) is remarkably high. Our density functional theory calculations identified two independent Weyl points near Fermi level besides the Kramers-Weyl nodes, which may contribute to the unusual critical field behavior. These findings demonstrate that TaGe2 is a promising material for exploring the interplay among chirality, superconductivity, and nontrivial topology.

Source-reported materials — not catalogue approval

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