Heavy-fermion behavior and the single-ion Kondo model

Abstract

Measurements of the temperature and concentration dependence of the specific heat, magnetic susceptibility, and electrical resistivity for Cei-x La^Pb3 are presented. The data scale with the concentration of Ce ions over surprisingly large intervals of x and T. The low-temperature specific heat per Ce ion agrees quantitatively with that of an S -j Kondo impurity of 7^ = 3.3 K. These results strongly suggest that intersite correlations do not play the expected important role and that the high specific heat y reported for CePl>3 is mainly a manifestation of the single-ion Kondo resonance. PACS numbers: 72.15.Qm, 75.20.Hr, 75.50.EeWithin condensed matter physics, one of the most exciting problems to have emerged during the last several years has been to understand the perplexing properties of heavy-fermion (HF) systems 1 " 3 and their relation to the broader issue of magnetic-moment formation. Characteristic of heavy fermions is an unusually large electronic specific heat at low temperatures, C -yT, where y corresponds to a very high density of states at the Fermi level or equivalently to an effective electron mass of 10 2 -10 3 times that of the free-electron mass. As a consequence of the large density of states these systems typically have a large Pauli susceptibility. The temperature dependence of C and X can be explained in terms of narrow resonant levels or a narrow band with a typical width of a few millielectronvolts or less. This narrow peak in the density of states has been attributed 2 ' 3 to a Kondo resonance, to hybridization effects and to Fermi-liquid properties, and its formation is still to be understood. Heavy-fermion behavior occurs in a variety of Ce-, Np-, U-, or Yb-based (concentrated or dilute) alloys and stoichiometric compounds.The low-temperature transport properties of stoichiometric HF compounds differ from those of alloys, while at high T, they are very similar. In compounds, the resistivity initially increases as one lowers T (which can be attributed to the Kondo effect), then goes through a large maximum and shows a sharp decrease at very low T. Both features, the existence of a maximum and the high resistivity at this maximum, are uncommon to normal metals. The rapid decrease of p(T) at low T is caused by a transition from incoherent to coherent scattering of the conduction electrons by the rare-earth (actinide) ions.

Anomalous compression behavior in lanthanum/cerium-based metallic glass under high pressure

“…Some reports indicate that the temperature dependence of resistivity for magnetic and nonmagnetic metallic glasses can be fitted to T 1/2 with a negative slope as predicted by Coulomb electron-electron interaction theories (48). In Ce-bearing crystalline alloys (25,26,43) a magnetic Kondo effect is usually suggested to explain the anomalous negative coefficient with a logarithmic temperature dependence at low temperature. Both effects mentioned above predict a magnetic field dependence of resistivity (49)(50)(51)(52).…”

“…Cerium is also the only pure element to exhibit a solid-solid critical point in the well known ␥ N ␣ isostructural phase transition (23,24). Many cerium-bearing alloys are heavy-fermion compounds and have anomalous low-temperature resistivity and magnetization behaviors that are relevant to Kondo coupling (25,26) and also have first-order phase transitions resembling the ␥ N ␣ phase transition for pure cerium or second-order phase transitions above a critical point (27). Recently, a LaCe-based BMG with a maximum size up to 10 mm (28) and a La-based BMG with a maximum size up to 20 mm were developed (29).…”

Universal zero-bias conductance for the single-electron transistor

“…1 Once a daunting theoretical challenge, the Anderson Hamiltonian yielded to an essentially exact numerical diagonalization, 2 followed by an exact analytical diagonalization. 3,4 From these and alternative approaches, physical properties were extracted, which eased the interpretation of experimental data, 5 theoretical results provided unifying views of apparently unrelated phenomena, 6 quantitative comparisons brought forth novel perceptions, 7 and dissections of the Anderson model brought to light the physics of nanoscale devices. [8][9][10][11][12] The last ten years were remarkably fruitful.…”

Low-temperature resistivity and thermoelectric power controlled by defects in the USb antiferromagnet

“…On the other hand, the low-temperature »…T † minimum (Franck et al 1961), accompanied eventually by the resistivity maximum on the low-temperature side (MacDonald et al 1962, Lin et al 1987, Schlottmann 1989) is a well known feature observed for single-ion Kondo systems. In these cases the low-temperature resistivity maximum shows the onset of the coherence eOE ect for a high Kondo impurity concentration.…”