Quadrupolar Kondo effect in uranium heavy-electron materials?

Cox, D. L.

doi:10.1103/physrevlett.59.1240

Cited by 686 publications

(525 citation statements)

References 31 publications

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“…Properties (Cu. [1][2][3][4][5], which are of a mainly qualitative nature and very robust, place very strong demands on any candidate explanations of the ZBA: the zero-bias anomalies disappear under annealing, and hence must be due to structural disorder; they disappear when static disorder is intentionally added, and hence cannot be due to static disorder -instead they must be due to dynamical impurities; they show no Zeeman splitting in a magnetic field (Cu.8b), and hence must be of non-magnetic origin. These observations lead to the proposal [1] that the zero-bias anomalies are due to nearly degenerate twolevel systems, interacting with conduction electrons according to the non-magnetic 2-channel Kondo model of Zawadowski [49], which renormalizes at low energies to the non-Fermi-liquid regime of the 2CK model.…”

Section: Conclusion a Summarymentioning

confidence: 99%

“…The study of systems of strongly correlated electrons that display non-Fermi-liquid behavior has attracted widespread interest in recent years, fueled in part by their possible relevance to heavy-fermion compounds [3,4,5] and high-T c superconductivity materials [6,7,8]. On the theoretical front, one of the consequences was a renewed interest in various multi-channel Kondo models, some of which were predicted by Nozières and Blandin [9] to contain non-Fermi-liquid physics.…”

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confidence: 99%

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The 2-Channel Kondo Model

et al. 1998

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Certain zero-bias anomalies (ZBAs) in the voltage, temperature and magnetic field dependence of the conductance G(V, T, H) of quenched Cu point contacts have previously been interpreted to be due to non-magnetic 2-channel Kondo (2CK) scattering from near-degenerate atomic two-level tunneling systems (Ralph and Buhrman, 1992;, and hence to represent an experimental realization of the non-Fermi-liquid physics of the T = 0 fixed point of the 2-channel Kondo model. In this, the first in a series of three papers (I,II,III) devoted to 2-channel Kondo physics, we present a comprehensive review of the quenched Cu ZBA experiments and their 2CK interpretation, including new results on ZBAs in constrictions made from Ti or from metallic glasses. We first review the evidence that the ZBAs are due to electron scattering from stuctural defects that are not static, but possess internal dynamics. In order to distinguish between several mechanisms proposed to explain the experiments, we then analyze the scaling properties of the conductance at low temperature and voltage and extract from the data a universal scaling function Γ(v). The theoretical calculation of the corresponding scaling function within the 2CK model is the subject of papers II and III. The main conclusion of our work is that the properties of the ZBAs, and most notably their scaling behavior, are in good agreement with the 2CK model and clearly different from several other proposed mechanisms.

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Section: Conclusion a Summarymentioning

confidence: 99%

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confidence: 99%

The 2-Channel Kondo Model

et al. 1998

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“…This would be the electric analogue of the exchange interaction between the magnetic dipole moments of Ce or U ions and the conduction electron spins that is widely believed to be responsible for the heavy fermion state in most Ce and U heavy fermion compounds. In fact, such a mechanism was proposed by Cox in 1987 [1] to account for the non-Fermi liquid temperature dependences of certain normal state physical properties of the heavy electron superconductor UBe 13 . The Pr compounds that display heavy fermion behavior include PrInAg 2 [2], PrFe 4 P 12 [3], and, possibly, PrFe 4 Sb 12 [4].…”

Section: Introductionmentioning

confidence: 99%

Superconductivity and the high-field ordered phase in the heavy-fermion compound PrOs₄Sb₁₂

Maple

Frederick

et al. 2003

J. Phys.: Condens. Matter

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Abstract.Superconductivity is observed in the filled skutterudite compound PrOs 4 Sb 12 below a critical temperature temperature T c = 1.85 K and appears to develop out of a nonmagnetic heavy Fermi liquid with an effective mass m * ≈ 50 m e , where m e is the free electron mass. Features associated with a cubic crystalline electric field are present in magnetic susceptibility, specific heat, electrical resistivity, and inelastic neutron scattering measurements, yielding a Pr 3+ energy level scheme consisting of a Γ 3 nonmagnetic doublet ground state, a low lying Γ 5 triplet excitied state at ∼ 10 K, and much higher temperature Γ 4 triplet and Γ 1 singlet excited states. Measurements also indicate that the superconducting state is unconventional and consists of two distinct superconducting phases. At high fields and low temperatures, an ordered phase of magnetic or quadrupolar origin is observed, suggesting that the superconductivity may occur in the vicinity of a magnetic or quadrupolar quantum critical point.

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“…[5][6][7][8][9][10][11] In these systems, it is possible that the ground states of the J multiplet split by the cubic crystalline electric field (CEF) are nonmagnetic, i.e., the matrix elements of the magnetic dipole J are identically zero, yet have a degeneracy that allows active higher-order multipoles such as electric quadrupoles or magnetic octupoles. Then various interesting phenomena such as multipole orders [12][13][14] or multichannel Kondo effects 15,16) are expected at low temperatures.These possibilities have indeed been realized in compounds containing Pr 3+ ions with the 4 f 2 electronic configuration. The nine states of the J = 4 ground multiplet are split by a cubic CEF into the Γ 1 nonmagnetic singlet, the Γ 3 nonmagnetic doublet, the Γ 4 magnetic triplet, and the Γ 5 magnetic triplet.…”

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NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

et al. 2016

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We report the results of 27 Al-NMR measurements on a single crystal of PrTi 2 Al 20 . This compound shows a phase transition near 2 K associated with the quadrupole degree of freedom of Pr ions, for which the ground state of the crystalline electric field is a nonmagnetic doublet. When a magnetic field is applied along the 111 direction, the NMR lines split upon entering the low-temperature phase, indicating the breaking of the three fold rotation symmetry due to the field-induced magnetic dipole perpendicular to the field. This provides microscopic evidence for a ferro order of the O 20 quadrupole. Although a first-order transition is expected theoretically, the line splitting evolves continuously within the experimental resolution.KEYWORDS: PrTi 2 Al 20 , NMR, quadrupole order, symmetry breaking Multipoles of f electrons in rare-earth compounds show a wide variety of phenomena. [1][2][3][4] In particular, non-Kramers rare-earth ions with an even number of f electrons in a cubic environment have been attracting strong interest recently. [5][6][7][8][9][10][11] In these systems, it is possible that the ground states of the J multiplet split by the cubic crystalline electric field (CEF) are nonmagnetic, i.e., the matrix elements of the magnetic dipole J are identically zero, yet have a degeneracy that allows active higher-order multipoles such as electric quadrupoles or magnetic octupoles. Then various interesting phenomena such as multipole orders [12][13][14] or multichannel Kondo effects 15,16) are expected at low temperatures.These possibilities have indeed been realized in compounds containing Pr 3+ ions with the 4 f 2 electronic configuration. The nine states of the J = 4 ground multiplet are split by a cubic CEF into the Γ 1 nonmagnetic singlet, the Γ 3 nonmagnetic doublet, the Γ 4 magnetic triplet, and the Γ 5 magnetic triplet. If the CEF ground state is the Γ 3 doublet, we encounter an interesting situation that the ground state is nonmagnetic but has nonzero matrix elements for the two types of quadrupoles, O 20 = (3J 2 z −J 2 )/2 and O 22 = √ 3(J 2 x −J 2 y )/2, and one octupole T xyz = ( √ 15/6)J x J y J z , where the bar represents the sum over the possible permutations of the indices x, y, and z. 13) The series of compounds PrT 2 X 20 (T : transition metal, X: Zn or Al) provides particularly interesting examples of the Γ 3 CEF ground states. 4) As shown in Fig. 1 [18][19][20][21] all of which also show superconductivity. [21][22][23][24][25][26] Various measurements indicate that the Al-based materials are characterized by stronger hybridization between conduction and f electrons than the Zn-based materials, leading to anomalous transport properties and their pronounced pressure depen- * E-mail : taka.taniguchi@issp.u-tokyo.ac.jp dence. 4,[23][24][25][26][27][28][29][30] In this paper, we focus on PrTi 2 Al 20 . The magnetic susceptibility for H 111 is nearly independent of temperature below 20 K, indicating van Vleck paramagnetism with a nonmagnetic CEF ground state. 29) Specific heat measurements ...

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Quadrupolar Kondo effect in uranium heavy-electron materials?

Cited by 686 publications

References 31 publications

The 2-Channel Kondo Model

The 2-Channel Kondo Model

Superconductivity and the high-field ordered phase in the heavy-fermion compound PrOs₄Sb₁₂

NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

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Quadrupolar Kondo effect in uranium heavy-electron materials?

Cited by 686 publications

References 31 publications

The 2-Channel Kondo Model

The 2-Channel Kondo Model

Superconductivity and the high-field ordered phase in the heavy-fermion compound PrOs4Sb12

NMR Observation of Ferro-Quadrupole Order in PrTi2Al20

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Superconductivity and the high-field ordered phase in the heavy-fermion compound PrOs₄Sb₁₂

NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀