Anisotropic superconductivity and unusually robust electronic critical field in single crystal La₇Ir₃

Unconventional superconductivity remains one of the most interesting problems in condensed matter physics. For all superconductors, the topology of the electronic band structure, along with the underlying crystal structure, play vital roles in determining the superconducting properties of the material. Systems lacking a centre of inversion exhibit a nonuniform lattice potential, giving rise to a Rashba-type antisymmetric spin-orbit coupling which allows for an admixture of singlet and triplet pairs. This may give rise to exotic superconducting band structures, time-reversal symmetry breaking and magnetoelectric effects such as upper critical fields that exceed the Pauli limit. The discovery of time-reversal symmetry breaking in the hexagonal noncentrosymmetric superconductor La₇Ir₃ [1] provided a large family of materials that may host exotic superconducting behaviours. Here we present our recent success in synthesising high-quality single crystals of La₇Ir₃ [2]. We also present experimental data on the unusually robust upper critical field as determined from electrical resistivity measurements in single crystals of La₇Ir₃.

[1] J. A. T. Barker et al., Phys. Rev. Lett. 115, 267001 (2015).

[2] D. A. Mayoh et al. Submitted (2021).