Evidence of d-wave pairing symmetry of the gap of the heavy-fermion superconductor CeIrIn5 from magnetic-penetration-depth measurements

The heavy-Fermion compounds $\text{Ce}T{\text{In}}_{5}$, where $T$ is Co, Ir, or Rh, exhibit two distinct superconducting regimes upon tuning the lattice density via doping or pressure. ${\text{CeIrIn}}_{5}$ is close to the boundary and there is some disagreement on whether its superconducting state is the same as ${\text{CeCoIn}}_{5}$ or not. In this Brief Report, we report the low-temperature penetration-depth $\ensuremath{\lambda}(T)$ measurements for ${\text{CeIrIn}}_{5}$. That $\ensuremath{\lambda}(T)\ensuremath{\propto}T$ below $0.3{T}_{c}$, irrespective of sample orientation, confirms the existence of line nodes in the gap with no evidence for the point node proposed in a hybrid-gap structure.