Observation of the Hybridization Gap and Fano Resonance in the Kondo Lattice<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>URu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Si</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Park, W. K.; Tobash, Paul H.; Ronning, F.; Bauer, E. D.; Sarrao, J. L.; Thompson, J. D.; Greene, L. H.

doi:10.1103/physrevlett.108.246403

Cited by 80 publications

(115 citation statements)

References 57 publications

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“…Schmidt et al (12) find a light band crossing the Fermi surface above 17.5 K turning into a hybridized heavy band only below the hidden-order transition. This finding contradicts the conventional view that mass builds up gradually below T K , although there have been recent reports of some hybridization occurring in the 25-30 K region by Park et al (14) and Levallois et al (15), but the reported effects are weak and perhaps not resolved by all spectroscopies. We can test the development of mass by carefully tracking the Drude weight as a function of temperature with optical spectroscopy.…”

contrasting

confidence: 55%

Optical spectroscopy shows that the normal state of URu ₂ Si ₂ is an anomalous Fermi liquid

Nagel

Uleksin

Rõõm

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Fermi showed that, as a result of their quantum nature, electrons form a gas of particles whose temperature and density follow the so-called Fermi distribution. As shown by Landau, in a metal the electrons continue to act like free quantum mechanical particles with enhanced masses, despite their strong Coulomb interaction with each other and the positive background ions. This state of matter, the Landau-Fermi liquid, is recognized experimentally by an electrical resistivity that is proportional to the square of the absolute temperature plus a term proportional to the square of the frequency of the applied field. Calculations show that, if electron-electron scattering dominates the resistivity in a LandauFermi liquid, the ratio of the two terms, b, has the universal value of b = 4. We find that in the normal state of the heavy Fermion metal URu 2 Si 2 , instead of the Fermi liquid value of 4, the coefficient b = 1 ± 0.1. This unexpected result implies that the electrons in this material are experiencing a unique scattering process. This scattering is intrinsic and we suggest that the uranium f electrons do not hybridize to form a coherent Fermi liquid but instead act like a dense array of elastic impurities, interacting incoherently with the charge carriers. This behavior is not restricted to URu 2 Si 2 . Fermi liquid-like states with b ≠ 4 have been observed in a number of disparate systems, but the significance of this result has not been recognized.hidden order | resistance | infrared conductivity | resonant scattering A mong the heavy Fermion metals, URu 2 Si 2 is one of the most interesting: it displays, in succession, no fewer than four different behaviors. As is shown in Fig. 1, where the electrical resistivity is plotted as a function of temperature, at 300 K the material is a very bad metal in which the conduction electrons are incoherently scattered by localized uranium f electrons. Below T K ∼ 75 K, the resistivity drops and the material resembles a typical heavy Fermion metal (1-3). At T 0 = 17.5 K the "hiddenorder" phase transition gaps a substantial portion of the Fermi surface but the nature of the order parameter is not known. A number of exotic models for the ordered state have been proposed (4-7), but there is no definitive experimental evidence to support them. Finally, at 1.5 K URu 2 Si 2 becomes an unconventional superconductor. The electronic structure, as shown by both angle-resolved photoemission experiments (8) and bandstructure calculations (9) is complicated, with several bands crossing the Fermi surface. To investigate the nature of the hidden-order state we focus on the normal state just above the transition. This approach has been used in the high-temperature superconductors where the normal state shows evidence of discrete frequency magnetic excitations that appear to play the role that phonons play in normal superconductors (10). The early optical experiments of Bonn et al. (11) showed that URu 2 Si 2 at 20 K, above the hidden order transition, has an infrared spectrum consisting ...

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contrasting

confidence: 55%

Optical spectroscopy shows that the normal state of URu ₂ Si ₂ is an anomalous Fermi liquid

Nagel

Uleksin

Rõõm

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…(1)] reveals the existence of an almost temperature-independent hybridization gap shifted from the Fermi-energy [19] and a pseudo-gap at the Fermi-energy which rapidly appears below the transition temperature [20]. …”

Section: An Approximate Ground Statementioning

confidence: 99%

Unusual Magnetic Field-Dependence of the Electronic Dispersion Relations in a Hidden Ordered Phase.

Riseborough

Magalhães²,

Calegari³

2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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The Hund's rule exchange interaction promotes a second-order phase transition to a coupled spin and orbital density wave state in the underscreened Anderson Lattice Model. The spin-flip part of the Hund's rule coupling stabilizes a spontaneous spin-dependent mixing of 5f quasiparticle bands that, in the normal state, have pure orbital characters. The transition breaks the spin-rotational invariance and leads to an asymmetric pseudo-gap which forms in the density of states. When a magnetic field is applied, the electronic dispersion relations become dependent on the relative orientation of the field and the spontaneously-chosen quantization axis. We argue that this may result in the magnetic susceptibility of the low-temperature phase becoming anisotropic, but without the development of a static magnetization.

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“…Their enhanced effective masses (m * = 8 − 25m 0 ) 7,8 cannot adequately be described by band structure calculations (m b ≤ 8m 0 ) 7 although the latter give a Fermi surface sheet topology in agreement with dHvA and SdH experiments 1,6 . Conceptually mass enhancement can be obtained within the Anderson lattice model in constrained mean field approximation 38 which also leads to a narrow indirect hybridization gap close to the Fermi level, equivalent to the Kondo temperature (T K 11.1 meV or 129 K) that can be seen in STM experiments 20,39 . Here we are primarily interested in the very low energy magnetic response of the heavy quasiparticle ω ∆ HO = 4.1 meV which is considerably smaller than the Kondo temperature T K = 2.7∆ HO .…”

Section: Two Orbital Model For Hidden Order and Heavy Quasiparticmentioning

confidence: 99%

Collective spin resonance excitation in the gapped itinerant multipole hidden order phase ofURu2Si2

Akbari

Thalmeier

2015

Phys. Rev. B

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An attractive proposal for the hidden order (HO) in the heavy electron compound URu2Si2 is an itinerant multipole order of high rank. It is due to the pairing of electrons and holes centered on zone center and boundary, respectively in states that have maximally different total angular momentum components. Due to the pairing with commensurate zone boundary ordering vector the translational symmetry is broken and a HO quasiparticle gap opens below the transition temperature THO. Inelastic neutron scattering (INS) has demonstrated that for T < THO the collective magnetic response is dominated by a sharp spin exciton resonance at the ordering vector Q that is reminiscent of spin exciton modes found inside the gap of unconventional superconductors and Kondo insulators. We use an effective two-orbital tight binding model incorporating the crystalline electric field effect to derive closed expressions for quasiparticle bands reconstructed by the multipolar pairing terms. We show that the magnetic response calculated within that model exhibits the salient features of the resonance found in INS. We also use the calculated dynamical susceptibility to explain the low temperature NMR relaxation rate.

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Observation of the Hybridization Gap and Fano Resonance in the Kondo LatticeURu2Si2

Cited by 80 publications

References 57 publications

Optical spectroscopy shows that the normal state of URu ₂ Si ₂ is an anomalous Fermi liquid

Optical spectroscopy shows that the normal state of URu ₂ Si ₂ is an anomalous Fermi liquid

Unusual Magnetic Field-Dependence of the Electronic Dispersion Relations in a Hidden Ordered Phase.

Collective spin resonance excitation in the gapped itinerant multipole hidden order phase ofURu2Si2

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Observation of the Hybridization Gap and Fano Resonance in the Kondo LatticeURu2Si2

Cited by 80 publications

References 57 publications

Optical spectroscopy shows that the normal state of URu 2 Si 2 is an anomalous Fermi liquid

Optical spectroscopy shows that the normal state of URu 2 Si 2 is an anomalous Fermi liquid

Unusual Magnetic Field-Dependence of the Electronic Dispersion Relations in a Hidden Ordered Phase.

Collective spin resonance excitation in the gapped itinerant multipole hidden order phase ofURu2Si2

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Product

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Optical spectroscopy shows that the normal state of URu ₂ Si ₂ is an anomalous Fermi liquid

Optical spectroscopy shows that the normal state of URu ₂ Si ₂ is an anomalous Fermi liquid