193,765 research outputs found
Unified character of correlation effects in unconventional Pu-based superconductors and \delta-Pu
Electronic structure calculations combining the local-density approximation
with an exact diagonalization of the Anderson impurity model show an
intermediate 5f^5-5f^6-valence ground state and delocalization of the 5f^5
multiplet of the Pu atom 5f-shell in PuCoIn_5, PuCoGa_5, and \delta-Pu. The
5f-local magnetic moment is compensated by a moment formed in the surrounding
cloud of conduction electrons. For PuCoGa_5 and \delta-Pu the compensation is
complete and the Anderson impurity ground state is a singlet. For PuCoIn_5 the
compensation is partial and the Pu ground state is magnetic. We suggest that
the unconventional d-wave superconductivity is likely mediated by the 5f-states
antiferromagnetic fluctuations in PuCoIn_5, and by valence fluctuations in
PuCoGa_5.Comment: 5 pages, 3 figure
Small Energy Scale for Mixed-Valent Uranium Materials
We investigate a two-channel Anderson impurity model with a magnetic
and a quadrupolar ground doublet, and a excited triplet. Using
the numerical renormalization group method, we find a crossover to a non-Fermi
liquid state below a temperature varying as the triplet-doublet
splitting to the 7/2 power. To within numerical accuracy, the non-linear
magnetic susceptibility and the contribution to the linear
susceptibility are given by universal one-parameter scaling functions. These
results may explain UBe as mixed valent with a small crossover scale
.Comment: 4 pages, 3 figures, REVTeX, to appear in Phys. Rev. Let
Itinerant U 5f band states in the layered compound UFeGa5 observed by soft X-ray angle-resolved photoemission spectroscopy
We have performed angle-resolved photoemission spectroscopy (ARPES)
experiments on paramagnetic UFeGa5 using soft X-ray synchrotron radiation
(hn=500eV) and derived the bulk- and U 5f-sensitive electronic structure of
UFeGa5. Although the agreement between the experimental band structure and the
LDA calculation treating U 5f electrons as being itinerant is qualitative, the
morphology of the Fermi surface is well explained by the calculation,
suggesting that the U 5f states can be essentially understood within the
itinerant-electron model.Comment: 13 pages, 4 figur
Spectral Properties of delta-Plutonium: Sensitivity to 5f Occupancy
By combining the local density approximation (LDA) with dynamical mean field
theory (DMFT), we report a systematic analysis of the spectral properties of
-plutonium with varying occupancy. The LDA Hamiltonian is
extracted from a tight-binding (TB) fit to full-potential linearized augmented
plane-wave (FP-LAPW) calculations. The DMFT equations are solved by the exact
quantum Monte Carlo (QMC) method and the Hubbard-I approximation. We have shown
for the first time the strong sensitivity of the spectral properties to the
occupancy, which suggests using this occupancy as a fitting parameter in
addition to the Hubbard . By comparing with PES data, we conclude that the
``open shell'' configuration gives the best agreement, resolving the
controversy over ``open shell'' versus ``close shell'' atomic
configurations in -Pu.Comment: 6 pages, 2 embedded color figures, to appear in Physical Review
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