Non fermi liquid behavior in strongly correlated f-electron materials (original) (raw)
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Evidence for a common physical description of non-Fermi-liquid behavior in f-electron systems
1998
The non-Fermi-liquid (NFL) behavior observed in the low temperature specific heat C(T)C(T)C(T) and magnetic susceptibility chi(T)\chi(T)chi(T) of f-electron systems is analyzed within the context of a recently developed theory based on Griffiths singularities. Measurements of C(T)C(T)C(T) and chi(T)\chi(T)chi(T) in the systems Th1−xUxPd2Al3Th_{1-x}U_{x}Pd_{2}Al_{3}Th1−xUxPd2Al3, Y1−xUxPd3Y_{1-x}U_{x}Pd_3Y1−xUxPd3, and UCu5−xMxUCu_{5-x}M_{x}UCu5−xMx (M = Pd, Pt) are found to be consistent with C(T)/Tproptochi(T)proptoT−1+lambdaC(T)/T \propto \chi(T) \propto T^{-1+\lambda}C(T)/Tproptochi(T)proptoT−1+lambda predicted by this model with lambda<1\lambda <1lambda<1 in the NFL regime. These results suggest that the NFL properties observed in a wide variety of f-electron systems can be described within the context of a common physical picture.
Disorder-driven non-Fermi liquid behaviour of correlated electrons
Reports on Progress in Physics, 2005
Systematic deviations from standard Fermi-liquid behavior have been widely observed and documented in several classes of strongly correlated metals. For many of these systems, mounting evidence is emerging that the anomalous behavior is most likely triggered by the interplay of quenched disorder and strong electronic correlations. In this review, we present a broad overview of such disorder-driven non-Fermi-liquid behavior, and discuss various examples where the anomalies have been studied in detail. We describe both their phenomenological aspects as observed in experiment, and the current theoretical scenarios that attempt to unravel their microscopic origin. 3. Spin-liquid behavior, destruction of the Kondo effect by bosonic dissipation, and fractionalization 4. Electron glasses, freezing in the charge sector, and the quantum AT line V. Conclusions and open problems
Non-Fermi Liquid Behavior and Griffiths Phase inf-Electron Compounds
Physical Review Letters, 1998
We study the interplay among disorder, RKKY and Kondo interactions in f-electron alloys. We argue that the non-Fermi liquid behavior observed in these systems is due to the existence of a Griffiths phase close to a quantum critical point. The existence of this phase provides a unified picture of a large class of materials. We also propose new experiments that can test these ideas.
Susceptibility inhomogeneity and non-Fermi liquid behavior in
Physica B: Condensed Matter, 2006
Transverse-field µSR shifts and relaxation rates have been measured in the non-Fermi liquid (NFL) alloy system UCu5−xPtx, x = 1.0, 1.5, and 2.5. At low temperatures the fractional spread in Knight shifts δK/K ≈ δχ/χ is 2 for x = 1, but is only half this value for x = 1.5 and 2.5. In a disorder-driven scenario where the NFL behavior is due to a broadly distributed (Kondo or Griffiths-phase cluster) characteristic energy E, our results indicate that δE/Eav ≈ (δK/K)T →0 is similar for UCu5−xPdx (x = 1 and 1.5) and UCu4Pt, but is reduced for UCu5−xPtx, x = 1.5 and 2.5. This reduction is due to a marked increase of E with increasing x; the spread δE is found to be roughly independent of x. Our results correlate with the observed suppression of other NFL anomalies for x > 1 in UCu5−xPtx but not in UCu5−xPdx, and are further evidence for the importance of disorder in the NFL behavior of both these alloy systems.
Journal of Physics: Condensed Matter, 2003
We report on electrical resistivity measurements performed on polycrystalline samples of UCu 5−x Ni x (x = 0.25, 1). In order to extract the Kondo contribution to the resistivity, the experiments were carried out over a wide temperature range (0.4-800 K). From the analysis of our results, we conclude that the Kondo temperature takes values of T K ∼ 240 K for x = 1 and T K ∼ 245 K for x = 0.25, and that for both Ni concentrations the dominant part of the remarkably high residual resistivity (ρ(0) ∼ 400 µ cm) corresponds to the Kondo contribution. These results are discussed in comparison with previous analysis of specific heat and magnetic susceptibility data that produced similar values of T K. We interpret our results in terms of disorder-driven non-Fermi liquid behaviour for UCu 4 Ni, as indicated by the anomalous temperature dependences of the electrical, thermal and magnetic properties previously observed in this compound.
Non-Fermi liquid behavior of the electrical resistivity at the ferromagnetic quantum critical point
We propose a model for the non-Fermi behavior in the proximity of the quantum phase transition induced by the strong polarization of the electrons due to local magnetic moments. The selfconsistent Renormalization Group methods have been used to calculate the temperature dependence of the electrical resistivity and specific heat. The T 5/3 dependence of resistivity and the T ln T dependence of the specific heat show that the magnetic impurities drive a ferromagnetic quantum phase transition and near the critical point the system present a non-Fermi liquid behavior. The model is in good agreement with the experimental data obtained for NixPd1−x alloy.
Resistivity of non-Galilean-invariant Fermi- and non-Fermi liquids
Lithuanian Journal of Physics, 2012
While it is well-known that the electron-electron (ee) interaction cannot affect the resistivity of a Galilean-invariant Fermi liquid (FL), the reverse statement is not necessarily true: the resistivity of a non-Galilean-invariant FL does not necessarily follow a T 2 behavior. The T 2 behavior is guaranteed only if Umklapp processes are allowed; however, if the Fermi surface (FS) is small or the electronelectron interaction is of a very long range, Umklapps are suppressed. In this case, a T 2 term can result only from a combined-but distinct from quantum-interference corrections-effect of the electron-impurity and ee interactions. Whether the T 2 term is present depends on 1) dimensionality [two dimensions (2D) vs three dimensions (3D)], 2) topology (simply-vs multiply-connected), and 3) shape (convex vs concave) of the FS. In particular, the T 2 term is absent for any quadratic (but not necessarily isotropic) spectrum both in 2D and 3D. The T 2 term is also absent for a convex and simply-connected but otherwise arbitrarily anisotropic FS in 2D. The origin of this nullification is approximate integrability of the electron motion on a 2D FS, where the energy and momentum conservation laws do not allow for current relaxation to leading-second-order in T /EF (EF is the Fermi energy). If the T 2 term is nullified by the conservation law, the first non-zero term behaves as T 4. The same applies to a quantum-critical metal in the vicinity of a Pomeranchuk instability, with a proviso that the leading (first non-zero) term in the resistivity scales as T D+2 3 (T D+8 3). We discuss a number of situations when integrability is weakly broken, e.g., by inter-plane hopping in a quasi-2D metal or by warping of the FS as in the surface states of topological insulators of the Bi2Te3 family. The paper is intended to be self-contained and pedagogical; review of the existing results is included along with the original ones wherever deemed necessary for completeness. I.
Marginal breakdown of the Fermi-liquid state on the border of metallic ferromagnetism
Nature, 2008
For the past half century, our understanding of how the interactions between electrons affect the low-temperature properties of metals has been based on the Landau theory of a Fermi liquid 1 . In recent times, however, there have been an increasingly large number of examples in which the predictions of the Fermi-liquid theory appear to be violated 2 . Although the qualitative reasons for the breakdown are generally understood, the specific quantum states that replace the Fermi liquid remain in many cases unclear. Here we describe an example of such a breakdown where the non-Fermi-liquid properties can be interpreted. We show that the thermal and electrical resistivities in high-purity samples of the d-electron metal ZrZn 2 at low temperatures have T and T 5/3 temperature dependences, respectively: these are the signatures of the 'marginal' Fermi-liquid state 3-7 , expected to arise from effective long-range spin-spin interactions in a metal on the border of metallic ferromagnetism in three dimensions 3,5 . The marginal Fermi liquid provides a link between the conventional Fermi liquid and more exotic non-Fermi-liquid states that are of growing interest in condensed matter physics. The idea of a marginal Fermi liquid has also arisen in other contextsfor example, in the phenomenology of the normal state of the copper oxide superconductors 7 , and in studies of relativistic plasmas and of nuclear matter 3,4,6 .
The non-Fermi-liquid behavior in magnetic Kondo lattices induced by peculiarities of spin dynamics
Physics Letters A, 2000
A scaling consideration of the Kondo lattices is performed with account of singularities in the spin excitation spectral Ž . function. It is shown that a non-Fermi-liquid NFL behaviour occurs naturally for complicated magnetic structures with several magnon branches. This may explain the fact that a NFL behaviour often takes place in the heavy-fermion systems with peculiar spin dynamics. The mechanisms proposed lead to some predictions about behaviour of specific heat, resistivity, magnetic susceptibility and anisotropy parameter, which can be verified experimentally. q 2000 Published by Elsevier Science B.V. All rights reserved. PACS: 75.30.Mb; 71.28 0375-9601r00r$ -see front matter q 2000 Published by Elsevier Science B.V. All rights reserved.