Non-Linear Susceptibility in U
 0.9
 Th
 0.1
 Be
 13
 : Evidence of a Transition from a Paramagnetic to a Quadrupolar Kondo Ground State

Aliev, F. G.; Mfarrej, H. El; Vieira, S.; Villar, R.; Martinez, J.L.

doi:10.1209/0295-5075/32/9/011

Cited by 29 publications

(43 citation statements)

References 22 publications

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“…In every case, the characteristic energy scale is too large for all of these mixed-valent runs to account for the experimental data. We conclude that the scenario of Aliev et al [6], suggesting that UBe 13 is more strongly mixed valent than anticipated previously, and that doping with Th increases the 5f 2 weight (driving the system closer to the quadrupolar Kondo limit), is qualitatively consistent with our results.…”

supporting

confidence: 93%

“…While the nonlinear magnetic susceptibility [5] is suggestive of a magnetic trivalent state, the rather weak temperature dependence of the linear susceptibility is more consistent with a nonmagnetic tetravalent state. Recently, following experiments on the nonlinear susceptibility of U 0.9 Th 0.1 Be 13 , Aliev et al [6] suggested a different physical regime, in which strong quantum fluctuations drive the uranium ions to a mixed-valent state.Here we explore the possibility of a mixed-valent state in the framework of the two-channel Anderson model [3], which consists of Γ 8 conduction electrons carrying both spin (σ =↑, ↓) and quadrupolar (α = ±) quantum labels, hybridizing via a matrix element V with a local uranium ion. The latter is modeled by a Γ 3 quadrupolar doublet in the 5f 2 configuration and a Γ 6 magnetic doublet in the 5f 3 configuration, separated in energy by ǫ f = E(5f 2 ) − E(5f 3 ).…”

mentioning

confidence: 99%

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Mixed-Valent Regime of the Two-Channel Anderson Impurity as a model forUBe13

Schiller

Anders²,

Cox³

1998

Phys. Rev. Lett.

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We investigate the mixed-valent regime of a two-configuration Anderson impurity model for uranium ions, with separate quadrupolar and magnetic doublets. With a new Monte Carlo approach and the non-crossing approximation we find: (i) A non-Fermi-liquid fixed point with two-channel Kondo model critical behavior; (ii) Distinct energy scales for screening the low-lying and excited doublets; (iii) A semi-quantitative explanation of magnetic-susceptibility data for U1−xThxBe13 assuming 60-70% quadrupolar doublet ground-state weight, supporting the quadrupolar-Kondo interpretation.PACS numbers: 75.20.Hr, 75.30.Mb, 71.27.+a Since the 1950's, Landau's Fermi-liquid theory has shaped our understanding of the metallic state. Based on the notion of a one-to-one mapping between the lowlying excitations of the interacting system and that of the noninteracting electron gas, the theory provides a remarkably robust scenario for the low-temperature properties of interacting electron systems. It is against this outstanding success that a growing class of f -shell materials -predominantly Ce-and U-based alloys -received considerable attention in recent years. Characterized by a logarithmically divergent linear coefficient of specific heat and anomalous temperature dependences of the resistivity and susceptibility, these materials appear to depart from the conventional Fermi-liquid scenario [1], thus challenging our understanding of metallic behavior.In this paper, we present results on the two-channel Anderson impurity model in the mixed-valent regime, motivated by the unusual nonlinear susceptibility data of the non-Fermi-liquid (NFL) alloy system U 1−x Th x Be 13 . The restricted Hilbert space of our model, a ground quadrupolar (non-Kramers) doublet in the 5f 2 configuration and a ground magnetic (Kramers) doublet in the 5f 3 configuration, renders it intractable to study by conventional Monte Carlo methods. We have developed a new Monte Carlo method based upon the mapping onto a Coulomb gas. We use this method to calibrate noncrossing approximation (NCA) results, which can then be extended to more extreme parameter regimes. We find that the model displays NFL physics characteristic of the two-channel Kondo model, even at the extreme mixed-valent limit when the two charge configurations are degenerate. We also find that two energy scales appear in the screening process away from the configurational degeneracy point. Using this model we are able to semi-quantitatively explain the linear and nonlinear susceptibility data by assuming 60-70% ground-state weight for the quadrupolar doublet, with the Th doping inducing a higher 5f 2 count, consistent with expectations from lattice constant data. We do not, however, explain the small energy scale for UBe 13 , and anticipate that dynamical inclusion of excited crystal field (CEF) levels in the 5f 2 configuration may remedy this problem. A proposed scenario for the NFL physics of UBe 13 involves the screening of uranium quadrupole moments in the 5f 2 configuration by conduction orbital ...

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supporting

confidence: 93%

mentioning

confidence: 99%

Mixed-Valent Regime of the Two-Channel Anderson Impurity as a model forUBe13

Schiller

Anders²,

Cox³

1998

Phys. Rev. Lett.

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“…configuration degeneracy with is lifted with Th substitution [28]. We refer the necessary intermediate valance calculation to a future work.…”

Section: +mentioning

confidence: 99%

Magnetoresistance in the Two-Channel Anderson Lattice

1997

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The paramagnetic phase of the two channel Anderson Lattice model in the Kondo limit is investigated in infinite spatial dimensions using the non-crossing approximation. The resistivity exhibits a Kondo upturn with decreasing T , followed by a slow decrease to a finite value at T = 0. The decrease reflects lattice coherence effects in concert with particle-hole symmetry breaking. The magneto-resistance obeys an approximate scaling relation, decreasing towards coherent Fermi liquid behavior with increasing field. The magnetic field induces a Drude peak in the optical conductivity. 75.30.Mb, 71.27.+a, 75.10.Dg

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“…The negative value of χ 3 was previously found in some non-Fermi liquid alloys, e.g., in Na x CoO 2 , which is believed to be close to a ferromagnetic quantum critical point [17]. In the case of UBe 13 [18], U 0:9 Th 0:1 Be 13 [19], and UCu 5 À x Pd x [20], the presence of nonlinear susceptibility was taken as an evidence for an electric quadrupole Kondo effect. However, the power-law dependence of the susceptibility presented above for x¼0.32 does not support a quadrupolar Kondo effect scenario, for which the susceptibility is expected to behave like χðTÞp ffiffiffi T p [21].…”

Section: Magnetic Susceptibility and Magnetizationmentioning

confidence: 73%

Magnetic phase diagram of pseudo-ternary solid solution URu1−xPdxGe

Gralak

Tran

2015

Journal of Solid State Chemistry

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Non-Linear Susceptibility in U _0.9 Th _0.1 Be ₁₃ : Evidence of a Transition from a Paramagnetic to a Quadrupolar Kondo Ground State

Abstract: We test the quadrupolar Kondo scenario in U0.9Th0.1Be13 by measurements of the non-linear susceptibility. We found our non-linear-susceptibility data to be consistent with a transition below T ∼ 6K from a magnetic (f3) to a quadrupolar (f2) doublet ground state of the U atom.

Cited by 29 publications

References 22 publications

Mixed-Valent Regime of the Two-Channel Anderson Impurity as a model forUBe13

Mixed-Valent Regime of the Two-Channel Anderson Impurity as a model forUBe13

Magnetoresistance in the Two-Channel Anderson Lattice

Magnetic phase diagram of pseudo-ternary solid solution URu1−xPdxGe

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Non-Linear Susceptibility in U 0.9 Th 0.1 Be 13 : Evidence of a Transition from a Paramagnetic to a Quadrupolar Kondo Ground State

Abstract: We test the quadrupolar Kondo scenario in U0.9Th0.1Be13 by measurements of the non-linear susceptibility. We found our non-linear-susceptibility data to be consistent with a transition below T ∼ 6K from a magnetic (f3) to a quadrupolar (f2) doublet ground state of the U atom.

Cited by 29 publications

References 22 publications

Mixed-Valent Regime of the Two-Channel Anderson Impurity as a model forUBe13

Mixed-Valent Regime of the Two-Channel Anderson Impurity as a model forUBe13

Magnetoresistance in the Two-Channel Anderson Lattice

Magnetic phase diagram of pseudo-ternary solid solution URu1−xPdxGe

Contact Info

Product

Resources

About

Non-Linear Susceptibility in U _0.9 Th _0.1 Be ₁₃ : Evidence of a Transition from a Paramagnetic to a Quadrupolar Kondo Ground State