Hexadecapolar Kondo Effect in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="bold">U</mml:mi><mml:msub><mml:mi>Ru</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="bold">S</mml:mi><mml:msub><mml:mi mathvariant="bold">i</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>?

Tóth, A.; Kotliar, Gabriel

doi:10.1103/physrevlett.107.266405

Cited by 18 publications

(11 citation statements)

References 27 publications

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“…The decay of the optical pumped state suggests the opening of a pseudogap below 25 K. Theoretical support for this idea was provided by Haraldsen et al (2011) who deduced the presence of a pseudogap state from PCS measurements. Toth and Kotliar (2011) proposed a localized hexadecapolar Kondo effect in diluted URu 2 Si 2 . Further, the most recent experimental studies on URu 2 Si 2 are by Niklowitz et al (2011), who performed quasielastic scattering from the Q 0 and Q 1 resonances, Bourdarot et al (2011), who performed neutron scattering under uniaxial stress, and Nagel et al (2011) who made a Fermi liquid analysis of the optical conductivity.…”

Section: Through the Swedish Research Council (Vr)mentioning

confidence: 99%

Colloquium: Hidden order, superconductivity, and magnetism: The unsolved case ofURu2Si2

2011

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This Colloquium reviews the 25 year quest for understanding the continuous (2 nd ) order, meanfield-like phase transition occurring at 17.5 K in URu 2 Si 2 . Since ca. ten years the term hidden order (HO) has been coined and utilized to describe the unknown ordered state, whose origin cannot be disclosed by conventional solid-state probes, such as x-rays, neutrons, or muons. HO is able to support superconductivity at lower temperatures (Tc ≈ 1.5 K) and when magnetism is developed with increasing pressure both the HO and the superconductivity are destroyed. Other ways of probing the HO are via Rh-doping and very large magnetic fields. During the last few years a variety of advanced techniques have been tested to probe the HO state and their attempts will be summarized. A digest of recent theoretical developments is also included. It is the objective of this survey to shed additional light on the HO state and its associated phases in other materials. VII. Present State of HO 12Acknowledgments 16 References 17Figures 21 I. HISTORICAL BACKGROUNDUranium is a most intriguing element, not only in itself but also as a basis for forming a variety of compounds and alloys with unconventional or puzzling physics properties (for recent reviews, see Sechovský and Havela (1998), Santini et al. (1999), Stewart (2006)). Natural or depleted uranium, i.e. containing 99.5 percent 238 U has a * Electronic address: mydosh@physics.leidenuniv.nl † Electronic address: peter.oppeneer@physics.uu.se mild alpha radioactivity of 25 kBq/g, which allows Ubased samples to be fabricated and studied in university laboratories with a minimum of safety precautions. Following initial discoveries of unexpected superconductivity and heavy-fermion behavior in uranium-based compounds as UBe 13 (Ott et al., 1983) and UPt 3 (Stewart et al., 1984) it has become popular to synthesize uranium compounds and to cool these in search for exotic ground states. Over the past 50 or so years many conducting and insulating systems were synthesized, analyzed and structurally characterized (Sechovský and Havela, 1998;Stewart, 2001Stewart, , 2006. The usual classification of the metallic samples at low temperature is superconducting and/or magnetic or with some of the modern compounds designated as "exotic" (Pfleiderer, 2009).Why are uranium-based materials so interesting? The observed variety of unusual behaviors derive directly from the U open 5f shell. Several defining electronic structure quantities of the U f electrons are all on the same energy scale: the exchange interaction, 5f bandwidth, the spin-orbit interaction, and intra-atomic f − f Coulomb interaction. As a consequence, i) elemental uranium displays intermediate behavior between the transition metals and the rare-earths in their characteristic bandwidths, yet it generates the largest spin-orbit coupling. ii) U lies directly on the border between localized and itinerant (or overlapping) 5f wavefunctions. iii) The WignerSeitz radii R WS of comparative elements places U near the minimum between metallic and...

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Section: Through the Swedish Research Council (Vr)mentioning

confidence: 99%

Colloquium: Hidden order, superconductivity, and magnetism: The unsolved case ofURu2Si2

2011

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“…Some of the earliest theories relied on the existence of a localized f 2 , J = 4 configuration to generate certain crystalline electric field (CEF) symmetries. Although CEF signatures have never been definitively observed, some recent innovative work once more depends on their existence, [7][8][9][10][11][12] while other work focuses on an itinerant model of the 5f electrons starting from a partially occupied f 3 orbital. 13,14 The DFT+DMFT calculations may form an interesting intermediate starting point, assigning the CEF states to the j = 5/2 shell and itinerant states to the j = 7/2 shell.…”

Section: Introductionmentioning

confidence: 99%

Probing5f-state configurations inURu2Si2with ULIII-edge reso

Booth¹,

Medling²,

Tobin³

et al. 2016

Phys. Rev. B

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Resonant x-ray emission spectroscopy (RXES) was employed at the U LIII absorption edge and the Lα1 emission line to explore the 5f occupancy, n f , and the degree of 5f orbital delocalization in the hidden order compound URu2Si2. By comparing to suitable reference materials such as UF4, UCd11, and α-U, we conclude that the 5f orbital in URu2Si2 is at least partially delocalized with n f = 2.87 ± 0.08, and does not change with temperature down to 10 K within the estimated error. These results place further constraints on theoretical explanations of the hidden order, especially those requiring a localized f 2 ground state.

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“…Since the crystalline symmetry of URu 2 Si 2 is tetragonal, the CEF states replacing the non-Kramers doublet is either Γ 5 doublet 64 with dipole moment along the c-axis, or two singlets. 36,65 If the splitting of singlets is smaller than T K in the latter case, the orbital Kondo effect can be effective 36,37 and the composite order may be formed. However, Ψ z and Ψ x , Ψ y are no longer degenerate.…”

Section: Diagonal Ordersmentioning

confidence: 99%

Composite electronic orders induced by orbital Kondo effect

Kuramoto

2016

Science Bulletin

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In a large number of rare-earth and actinide systems, Kondo effect tends to suppress magnetic order by making the spin singlet between localized and conduction electron spins. In the presence of orbital degrees of freedom, however, there emerge exotic electronic orders induced by Kondo effect. The orbital Kondo effect can collectively make diagonal and off-diagonal (superconducting) orders. With the particle-hole symmetry in conduction bands, these orders are all degenerate, forming a macroscopic SO(5) multiplet. This paper discusses recent theoretical development on these electronic orders which are relevant to Pr 3+ and U 4+ systems with even number of f electrons per site. In the superconducting order, each conduction-electron pair is coupled with local degrees of freedom, forming a composite entity with a staggered spatial pattern. The quasi-particle spectrum is best interpreted as virtual hybridization with resonant states at the Fermi level. Possible order parameter for URu2Si2 in the hidden order state is discussed in the context of composite orders. Briefly discussed are related issues such as homogeneous odd-frequency pairing and SO(5) theory for high-temperature superconductors.

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Hexadecapolar Kondo Effect inURu2Si2?

Cited by 18 publications

References 27 publications

Colloquium: Hidden order, superconductivity, and magnetism: The unsolved case ofURu2Si2

Colloquium: Hidden order, superconductivity, and magnetism: The unsolved case ofURu2Si2

Probing5f-state configurations inURu2Si2with ULIII-edge reso

Composite electronic orders induced by orbital Kondo effect

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