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Abstract
We use angle-resolved photoemission spectroscopy (ARPES) to image the emergence of substaintial dispersion anomalies in the electronic renormalization of the actinide compound UCoGa$_5$ which was presumed to belong to a conventional Fermi liquid family. Kinks or abrupt breaks in the slope of the quasiparticle dispersion are detected both at low ($\sim$130 meV) and high ($\sim$1 eV) binding energies below the Fermi energy, ruling out any significant contribution of phonons. We perform numerical calculations to demonstrate that the anomalies are adequately described by coupling between itinerant fermions and spin fluctuations arising from the particle-hole continuum of the spin-orbit split $5f$ states of uranium. These anomalies are resemble the `waterfall' phenomenon of the high-temperature copper-oxide superconductors, suggesting that spin fluctuations are a generic route toward multiform electronic phases in correlated materials as different as high-temperature superconductors and actinides.
Highlights
The coupling between electrons and elementary excitations, originating from lattice or electronic degrees of freedom, can drive the formation of new emergent phases, such as magnetism and superconductivity
We demonstrate that the electron-electron interaction due to the dynamical spin fluctuations of exchanged bosons can describe the data
Our intermediate Coulomb-coupling approach offers an opportunity to address the complex nature of the dynamic band renormalization in actinides
Summary
The coupling between electrons and elementary excitations, originating from lattice or electronic degrees of freedom, can drive the formation of new emergent phases, such as magnetism and superconductivity. For rare-earth and actinide f-electron systems, the development of lowenergy fermionic excitations with heavy electron mass is complicated by the interactions between f-electron spins and those of itinerant electrons They often exhibit an interplay between Kondo physics, magnetism, and superconductivity [1]. It has been thought that this physics is not at play in UCoGa5 with a tetragonal crystal structure and metallic ground state [2] It has been dubbed a vegetable, because of its lack of heavy mass [3,4], other competing orders [2,5,6,7], and showing of a spinlattice relaxation rate that obeys the Korringa law of a conventional Fermi liquid at low temperatures [8]. It offers a clean approach to unravel the nature of the exchanged boson in the actinide family and related heavy-fermion systems
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