Contrasting pressure evolution of f -electron hybridized states in CeRhIn5 and YbNi3Ga9 : An optical

Abstract

Optical conductivity [σ(ω)] of CeRhIn 5 and YbNi 3 Ga 9 have been measured at external pressures to 10 GPa and at low temperatures to 6 K. Regarding CeRhIn 5 , at ambient pressure the main feature in σ(ω) is a Drude peak due to free carriers. With increasing pressure, however, a characteristic mid-infrared (mIR) peak rapidly develops in σ(ω), and its peak energy and width increase with pressure. These features are consistent with an increased conduction (c)-f electron hybridization at high pressure, and show that the pressure has tuned the electronic state of CeRhIn 5 from very weakly to strongly hybridized ones. As for YbNi 3 Ga 9 , in contrast, a marked mIR peak is observed already at ambient pressure, indicating a strong c-f hybridization. At high pressures, however, the mIR peak shifts to lower energy and becomes diminished, and seems merged with the Drude component at 10 GPa. Namely, CeRhIn 5 and YbNi 3 Ga 9 exhibit some opposite tendencies in the pressure evolutions of σ(ω) and electronic structures. These results are discussed in terms of the pressure evolutions of c-f hybridized electronic states in Ce and Yb compounds, in particular in terms of the electron-hole symmetry often considered between Ce and Yb compounds.

Critical point anomalies in doped CeRhIn5

“…Here the hybridization is comparable to the pristine CeCoIn 5 , where the MIR peak occurs at 600 cm −1 [48]. The x = 9.8% compound exhibits a hybridization similar to the one obtained by applying 2 GPa external pressure [45].…”

“…All compounds possess a highly metallic nature in accord with the notably large dc conductivity values that reach the order of 10 4 ( cm) −1 . A weak hybridizing nature of pristine CeRhIn 5 is reported previously [43][44][45]; the behavior resembles other magnetically ordered heavy-fermion compounds like CeIn 3 due to weak Kondo coupling [31,40,46]. The hybridization gap in σ 1 (ω) forms at significantly lower energy compared to other strongly hybridizing compounds such as CeCoIn 5 [47].…”