| 1. |
- Dakovski, Georgi L., et al.
(author)
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Anomalous femtosecond quasiparticle dynamics of hidden order state in URu(2)Si(2)
- 2011
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:16, s. 161103-
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Journal article (peer-reviewed)abstract
- At T(0) = 17.5 K an exotic phase emerges from a heavy fermion state in URu(2)Si(2). The nature of this hidden order (HO) phase has so far evaded explanation. Formation of an unknown quasiparticle (QP) structure is believed to be responsible for the massive removal of entropy at the HO transition, however, experiments and ab initio calculations have been unable to reveal the essential character of the QP. Here we use femtosecond pump-probe time-and angle-resolved photoemission spectroscopy (tr-ARPES) to elucidate the ultrafast dynamics of the QP. We show how the Fermi surface is renormalized by shifting states away from the Fermi level at specific locations, characterized by vector q(< 110 >) = 0.56 +/- 0.08 angstrom(-1). Measurements of the temperature-time response reveal that, upon entering the HO, the QP lifetime in those locations increases from 42 fs to few hundred fs. The formation of the long-lived QPs is identified here as a principal actor of the HO.
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| 2. |
- Rusz, Jan, et al.
(author)
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Probing the electronic structure of pure and doped CeMIn5 (M=Co,Rh,Ir) crystals with nuclear quadrupolar resonance
- 2008
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:24, s. 245124-
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Journal article (peer-reviewed)abstract
- We report calculations of the electric-field gradients (EFGs) in pure and doped CeMIn5 (M=Co, Rh, and Ir) compounds and compare with experiment. The degree to which the Ce 4f electron is localized is treated within various models: the local-density approximation, generalized gradient approximation (GGA), GGA+U, and 4f-core approaches. We find that there is a correlation between the observed EFG and whether the 4f electron participates in the band formation or not. We also find that the EFG evolves linearly with Sn doping in CeRhIn5, suggesting the electronic structure is modified by doping. In contrast, the observed EFG in CeCoIn5 doped with Cd changes little with doping. These results indicate that nuclear quadrupolar resonance is a sensitive probe of electronic structure.
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