Quantum critical phenomena in undoped heavy-fermion metals

Abstract

We present results of low-temperature calorimetric and resistive measurements on the isostructural heavy-fermion compounds CeCu 2 Si 2 and CeNi 2 Ge 2 . 'Non-Fermi-liquid' effects are established which suggest the nearness of an antiferromagnetic quantum critical point (QCP) in both systems. The observed deviations from the properties of a Landau Fermi liquid (FL) may be related to anomalous energy dependences of both the quasiparticle mass and the quasiparticlequasiparticle scattering cross section. For CeNi 2 Ge 2 , a moderately heavy FL can be recovered by application of moderate values of either magnetic field or hydrostatic pressure. For p = 1.7 GPa a novel, non-superconducting, phase transition has been discovered at T 1 1 K.

Singular or non-Fermi liquids

“…The compound YbRh 2 S 2 seems to have similar properties [258]. Related properties have also been found in U 2 Pt 2 In [88,89] [250]. The SFL properties observed at the Mott insulator-to-metal transition in BaVS 3 [99] are also of related interest.…”

Disorder, inhomogeneity and spin dynamics in f-electron non-Fermi liquid systems

“…At ambient pressure these include CeCu 5.9 Au 0.1 [23][24][25], Ce(Ru 1−x Rh x ) 2 Si 2 , x ≈ 0.5 [26,27], CeNi 2 Ge 2 [28,29], and YbRh 2 Si 2 [30]. Thus one can compare spin dynamics in 'disordered' and 'ordered' materials.…”

Anomalous frequency and temperature-dependent scattering and Hund's coupling in the almost quantum critical heavy-fermion systemCeFe2Ge2

“…This behavior is reminiscent of other 4f-electron systems: CeRu 2 Si 2 [11], CeNi 2 Ge 2 [12] and CeCu 6 [13,14]. In addition to metamagnetic anomalies, deviations from ordinary FL behavior occur under certain circumstances [15][16][17] in these materials. CFG has been reported to show deviations from FL predictions; a T 1.5 dependence of resistivity in the temperature range ∼2-15 K is observed instead of the FL T 2 dependence.…”