Relocalization of Uranium 5f Electrons in Antiferromagnetic Heavy Fermion Superconductor UPd_2Al_3: Insights from Angle-Resolved Photoemission Spectroscopy
arxiv(2024)
摘要
We investigate the antiferromagnetic heavy fermion superconductor UPd2Al3,
employing angle-resolved photoemission spectroscopy to unravel the complex
electronic structure of its U 5f electrons. We observe unexpected
characteristics that challenge the conventional temperature-dependent behavior
of heavy fermion systems, revealing unexpected characteristics. At temperatures
above the anticipated coherence temperature (T^*), we observe itinerant U 5f
electrons at temperatures higher than previously postulated. Additionally, a
previously unidentified dispersionless band emerges around 600 meV below the
Fermi energy, potentially linked to spin-orbit splitting within the U 5f
states. Hybridization between the 5f electrons and conduction band was observed
with an energy dispersion of 10 meV at low temperatures, suggesting that U 5f
electrons near and at the Fermi surface have an itinerant nature.
Temperature-dependent 5d-5f resonance spectra reveal that the 5f electron
spectrum weight increases with lowering temperature and begins to decrease at
temperatures significantly higher than the Neel temperature (T_N). We further
show that the competition between the Kondo effect and
Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions may be responsible for the
relocalization of 5f electrons, making relocalization a precursor to the
establishment of magnetic order at lower temperatures. Our experiments also
provide evidence that 5f electrons with the same orbital are involved in both
the Kondo effect and RKKY interactions, suggesting that the two coexist at
lower temperatures.
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