A fundamental problem posed from the study of correlated electron compounds, of which heavy-fermion systems are prototypes, is the need to understand the physics of states near a quantum critical point (QCP). At a QCP, magnetic order is suppressed continuously to zero temperature and unconventional superconductivity often appears. Here, we report pressure (P)-dependent ¹¹⁵In nuclear quadrupole resonance (NQR) measurements on heavy-fermion antiferromagnet CeRh_0.5Ir_0.5In₅. These experiments reveal an antiferromagnetic (AF) QCP at \({P}_{{\rm{c}}}^{{\rm{AF}}}=1.2\) GPa where a dome of superconductivity reaches a maximum transition temperature T_c. Preceding \({P}_{{\rm{c}}}^{{\rm{AF}}}\), however, the NQR frequency ν_Q undergoes an abrupt increase at \({P}_{{\rm{c}}}^{{\rm{* }}}\) = 0.8 GPa in the zero-temperature limit, indicating a change from localized to itinerant character of cerium’s f-electron and associated small-to-large change in the Fermi surface. At \({P}_{{\rm{c}}}^{{\rm{AF}}}\) where T_c is optimized, there is an unusually large fraction of gapless excitations well below T_c that implicates spin-singlet, odd-frequency pairing symmetry.

从研究相关的电子化合物（其中的重费米子系统是原型）提出的一个基本问题是需要了解量子临界点（QCP）附近状态的物理学。在QCP上，磁阶被连续抑制到零温度，并且经常出现非常规的超导性。在这里，我们报告重金属费反铁磁体CeRh _0.5 Ir _0.5 In _5中依赖于压力（P）的¹¹⁵ In核四极共振（NQR）测量。这些实验揭示了在\（{P} _ {{\ rm {c}}} ^ {{\ rm {AF}}} = 1.2 \）  GPa的反铁磁（AF）QCP，其中超导圆顶达到了最高转变温度Ť _ç。前述\（{P} _ {{\ RM {C}}} ^ {{\ RM {AF}}} \），然而，NQR频率ν _Q处经历的突然增加\（{P} _ {{\ rm {c}}} ^ {{\ rm {*}}} \） =零温度范围内的0.8 GPa，表明铈的f电子从局部特征到迭代特征的变化以及相关的从小到大的变化费米表面。在优化了T _c的\（{P} _ {{\ rm {c}}} ^ {{\ rm {AF}}} \），在远低于T _c的无间隙激励中有很大一部分异常，这意味着自旋-单，奇频配对对称。