High-pressure effect on the electronic state in CeNiGe₃: pressure-induced superconductivity

Abstract

We have measured the electrical resistivity of an antiferromagnetic Kondo compound CeNiGe 3 under pressure. The Néel temperature initially increases with pressure P up to 3 GPa, then decreases rather steeply with further increasing pressure, and becomes zero at a critical pressure P c 5.5 GPa. The A and ρ 0 values of the resistivity ρ = ρ 0 + AT 2 in the Fermi liquid relation become maximum around P c , the A value attaining an extremely large value which is comparable with that in a heavy fermion superconductor CeCu 2 Si 2. Superconductivity is found below 0.48 K in a wide pressure region from 4 to 10 GPa. The upper critical field H c2 (0) is about 2 T, indicating heavy fermion superconductivity. In cerium and uranium compounds, the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction and the Kondo effect compete with each other [1, 2]. The competition between the RKKY interaction and the Kondo effect was discussed by Doniach [3] as a function of |J cf |D(ε F), where |J cf | is the magnitude of the magnetic exchange interaction and D(ε F) is the electronic density of states at the Fermi energy ε F. Most cerium compounds order magnetically when the RKKY interaction overcomes the Kondo effect at low temperatures. The magnetic ordering is formed by the localized-4f moments of Ce 3+. The topology of the Fermi surface for the conduction electrons is therefore quite similar to that of the corresponding non-4f lanthanum compounds, although the cyclotron mass of the cerium compounds is typically one to two orders of magnitude larger than that of the lanthanum compounds.

Thermodynamics Investigation on Pressure-induced Superconductor CeNiGe3by ac Calorimetry

“…studies. 7,9) There is no anomaly around 5.0 K in the present heat capacity, which is contrary to the neutron scattering experiment which showed the successive magnetic phase transitions at 5.5 and 5.0 K as described in the introduction.…”

The electronic structure of CeNiGe3 and YNiGe3 superconductors by ab initio calculations

“…Ce 2 Ni 3 Ge 5 [1,2] and CeNi 2 Ge 2 [3,4], however, the highest superconducting transition temperature T c (= 0.48 K) was reported for studied in this paper CeNiGe 3 [5]. It is known that the phenomenon of pressure-induced SC in such f-electron systems occurs around the quantum critical point (QCP), where their antiferromagnetic (AFM) order vanishes and the heavy-fermion (HF) state is formed.…”

Evolution of an Unconventional Superconducting State inside the Antiferromagnetic Phase of CeNiGe3 under Pressure: A 73Ge-Nuclear-Quadrupole-Resonance Study

“…10 The most remarkable feature is that P -induced superconductivity emerges in two P ranges of 1.7-3.7 GPa and 5.9-7.3 GPa, where zeroresistivity is observed.…”