Reemergent Superconductivity and Avoided Quantum Criticality in Cd-Doped ${\mathrm{CeIrIn}}_5$ under Pressure

We investigated the electrical resistivity and heat capacity of 1% Cd-doped ${\mathrm{CeIrIn}}_5$ under hydrostatic pressure up to 2.7 GPa, near where long-range antiferromagnetic order is suppressed and bulk superconductivity suddenly reemerges. The pressure-induced $T_c$ is close to that of pristine ${\mathrm{CeIrIn}}_5$ at 2.7 GPa, and no signatures of a quantum critical point under pressure support a local origin of the antiferromagnetic moments in $\mathrm{Cd}\text{−}{\mathrm{CeIrIn}}_5$ at ambient pressure. Similarities between superconductors ${\mathrm{CeIrIn}}_5$ and ${\mathrm{CeCoIn}}_5$ in response to Cd substitutions suggest a common magnetic mechanism.

Figure 1

Pressure evolution of (a) electrical resistivity between 1.8 and 300 K; (b) electrical resistivity between 0.4 and 4 K; (c) heat capacity of 1% Cd doped ${\mathrm{CeIrIn}}_5$. The heat capacity curves measured by ac calorimetry are in arbitrary units and shifted vertically for clarity, while the low temperature data ($T<1\mathrm{K}$) for $P\le 2.39\mathrm{GPa}$ have no additional transitions and are not shown to avoid confusion. The dashed line in (c) is a guide to eyes to track the AFM $T_N$ evolution under pressures and the superconducting transitions are marked by $\star$ for 2.53 and 2.70 GPa.

Figure 2

Temperature-pressure ($T\text{−}P$) phase diagram of 1% $\mathrm{Cd}\text{−}{\mathrm{CeIrIn}}_5$. The AFM $T_N$ is determined by ac calorimetry while superconducting transition temperatures $T_c$ determined by resistivity and heat capacity show distinctive pressure behaviors. SC regions above 2.7 GPa are assumed as guide to eyes and a $T_c$ curve for pristine ${\mathrm{CeIrIn}}_5$ under pressure [28] is included for comparison.

Figure 3

The temperature-pressure contour color plot of resistivity for 1.0% Cd-doped ${\mathrm{CeIrIn}}_5$ with both AFM and resistive SC boundaries included. The dashed line is a guide to eyes to track the pressure evolution of the Kondo lattice coherence temperature.

Figure 4

3D plot of the temperature-doping-pressure phase diagram of ${\mathrm{CeIrIn}}_5$, where AFM (empty circles) and SC (solid circles) phases compete or coexist. The dotted lines are guides to eyes to track the pressure evolution of AFM or SC in different samples, i.e., 1.0% Cd-doped, pure, 40% Rh-doped ${\mathrm{CeIrIn}}_5$, and pure ${\mathrm{CeRhIn}}_5$. The doping phase diagram at 2.7 GPa is constructed based on smooth extrapolations of our results and those in [15, 19, 25, 32].