Abstract Reflection Electron Energy Loss Spectra (REELS) have been acquired on plutonium δ-Pu-Ga ... more Abstract Reflection Electron Energy Loss Spectra (REELS) have been acquired on plutonium δ-Pu-Ga alloys, α-Pu2O3 and PuO2. The position of the peaks attributable to the Pu 6p excitation can be used as ‘fingerprint’ for these species. X-ray Photoelectron Spectroscopy has been used to aid interpretation of the REELS spectra. The band gap of PuO2 was determined from the onset of the energy loss in the REELS spectrum. The REELS data have been evaluated within the dielectric response theory by means of the QUEELS-∊(k, w)-REELS software [Surf. Interface Anal. 36, (2004) 824]. The Energy Loss Function, dielectric function, refractive index and extinction coefficient for these materials have been determined in the ultraviolet and extreme ultraviolet range and are compared to previously reported results. Crown copyright (C) 2021 Published by Elsevier B. V. All rights reserved.
ABSTRACT A recent paper on photoemission of YbInCu4 reports some significant findings that have i... more ABSTRACT A recent paper on photoemission of YbInCu4 reports some significant findings that have implications beyond the single material investigated. We find some of the experimental results in the paper to be meritorious but the central premise and conclusion are not supported by additional data. We provide alternative interpretations for the experimental results and exploit advantages in the photoemission process to more clearly elucidate the electronic structure of Yb heavy fermions and the applicability of photoelectron spectroscopy.
We have developed the Angle Resolved Photoemission Spectroscopy (ARPES) system for transuranic ma... more We have developed the Angle Resolved Photoemission Spectroscopy (ARPES) system for transuranic materials. The ARPES transuranic system is an endstation upgrade to the Laser Plasma Light Source (LPLS) at Los Alamos National Laboratory. The LPLS is a tunable light source for photoemission with a photon energy range covering the vacuum ultraviolet (VUV) and soft x-ray regions (27-140 eV). The LPLS was designed and developed for transuranic materials. Transuranic photoemission is currently not permitted at the public synchrotrons worldwide in the VUV energy range due to sample encapsulation requirements. With the addition of the ARPES capability to the LPLS system there is an excellent opportunity to explore new details centered on the electronic structure of actinide and transuranic materials.
ABSTRACTMany metallic actinide systems host partially filled 5f electrons in the low-energy spect... more ABSTRACTMany metallic actinide systems host partially filled 5f electrons in the low-energy spectrum. Consequently, they exhibit diverse quantum mechanical phenomena such as magnetism, superconductivity, a mysterious hidden-order phase, or heavy-fermion behavior. Here we present results of a unified theoretical method based on the self-consistent GW formalism for the electronic many-body self-energy. We calculate the dynamic electronic correlation spectra starting from materials specific first-principles electronic band-structure. In particular, we present results for four isostructural intermetallic actinides PuCoIn5, PuCoGa5, PuRhGa5, and UCoGa5. A common underlying property of these materials is a strong spin–orbit coupling split band structure that enables substantial spin fluctuations. In a feedback effect on the electronic structure they create electronic ‘hot spots’, where the single-particle spectral weight is maximum, resulting in a universal peak-dip-hump feature. These re...
The electronic structure of the Pu-based superconductor PuCoGa5 and the Pauli paramagnet UCoGa5 i... more The electronic structure of the Pu-based superconductor PuCoGa5 and the Pauli paramagnet UCoGa5 is investigated using photoemission spectroscopy. The photoemission data of PuCoGa5 reveal features at the Fermi energy EF and about 1-1.5 eV below EF indicative of itinerant and localized f-electrons, respectively. Angle-resolved spectra of UCoGa5 show two peaks at similar energies that are highly dispersive, providing evidence for itinerant character of the f-electrons in this material. A comparison of the PuCoGa5 and UCoGa5 data to the spectra of α-Pu and δ-Pu serves to place PuCoGa5 within the context of the more general electronic structure problem in elemental Pu.
The 5f electronic states in elemental Pu and Pu compounds exhibit elements of both itinerant and ... more The 5f electronic states in elemental Pu and Pu compounds exhibit elements of both itinerant and localized behavior. Several first-principles calculations have been presented to describe this balance, differing in the manner in which electron correlation is included in the calculation. This paper describes a calculations performed with the Mixed Level Model (MLM), presenting calculated results for the two Pu compounds, PuRhGa5 and PuCoGa5. The MLM results are compared with other calculations and the differences discussed.
The Chemistry of the Actinide and Transactinide Elements
Page 1. CHAPTER TWENTY ONE 5f‐ELECTRON PHENOMENA IN THE METALLIC STATE AJ Arko, John J. Joyce, an... more Page 1. CHAPTER TWENTY ONE 5f‐ELECTRON PHENOMENA IN THE METALLIC STATE AJ Arko, John J. Joyce, and Ladia Havela 21.1 INTRODUCTION In this chapter, the properties of actinides in the metallic state will be ...
Single crystal antiferromagnetic USb2 was studied at 15K by angle-resolved photoemission in the p... more Single crystal antiferromagnetic USb2 was studied at 15K by angle-resolved photoemission in the photon energy range between 20 eV and 110 eV. The overall energy resolution for lowest energy range was 20 meV, and the momentum resolution was 0.09A-1. The sharp photoemission peak (FWHM 30-50 meV) near the Fermi edge (EF) and Laue patterns confirmed the high quality of the
Abstract Reflection Electron Energy Loss Spectra (REELS) have been acquired on plutonium δ-Pu-Ga ... more Abstract Reflection Electron Energy Loss Spectra (REELS) have been acquired on plutonium δ-Pu-Ga alloys, α-Pu2O3 and PuO2. The position of the peaks attributable to the Pu 6p excitation can be used as ‘fingerprint’ for these species. X-ray Photoelectron Spectroscopy has been used to aid interpretation of the REELS spectra. The band gap of PuO2 was determined from the onset of the energy loss in the REELS spectrum. The REELS data have been evaluated within the dielectric response theory by means of the QUEELS-∊(k, w)-REELS software [Surf. Interface Anal. 36, (2004) 824]. The Energy Loss Function, dielectric function, refractive index and extinction coefficient for these materials have been determined in the ultraviolet and extreme ultraviolet range and are compared to previously reported results. Crown copyright (C) 2021 Published by Elsevier B. V. All rights reserved.
ABSTRACT A recent paper on photoemission of YbInCu4 reports some significant findings that have i... more ABSTRACT A recent paper on photoemission of YbInCu4 reports some significant findings that have implications beyond the single material investigated. We find some of the experimental results in the paper to be meritorious but the central premise and conclusion are not supported by additional data. We provide alternative interpretations for the experimental results and exploit advantages in the photoemission process to more clearly elucidate the electronic structure of Yb heavy fermions and the applicability of photoelectron spectroscopy.
We have developed the Angle Resolved Photoemission Spectroscopy (ARPES) system for transuranic ma... more We have developed the Angle Resolved Photoemission Spectroscopy (ARPES) system for transuranic materials. The ARPES transuranic system is an endstation upgrade to the Laser Plasma Light Source (LPLS) at Los Alamos National Laboratory. The LPLS is a tunable light source for photoemission with a photon energy range covering the vacuum ultraviolet (VUV) and soft x-ray regions (27-140 eV). The LPLS was designed and developed for transuranic materials. Transuranic photoemission is currently not permitted at the public synchrotrons worldwide in the VUV energy range due to sample encapsulation requirements. With the addition of the ARPES capability to the LPLS system there is an excellent opportunity to explore new details centered on the electronic structure of actinide and transuranic materials.
ABSTRACTMany metallic actinide systems host partially filled 5f electrons in the low-energy spect... more ABSTRACTMany metallic actinide systems host partially filled 5f electrons in the low-energy spectrum. Consequently, they exhibit diverse quantum mechanical phenomena such as magnetism, superconductivity, a mysterious hidden-order phase, or heavy-fermion behavior. Here we present results of a unified theoretical method based on the self-consistent GW formalism for the electronic many-body self-energy. We calculate the dynamic electronic correlation spectra starting from materials specific first-principles electronic band-structure. In particular, we present results for four isostructural intermetallic actinides PuCoIn5, PuCoGa5, PuRhGa5, and UCoGa5. A common underlying property of these materials is a strong spin–orbit coupling split band structure that enables substantial spin fluctuations. In a feedback effect on the electronic structure they create electronic ‘hot spots’, where the single-particle spectral weight is maximum, resulting in a universal peak-dip-hump feature. These re...
The electronic structure of the Pu-based superconductor PuCoGa5 and the Pauli paramagnet UCoGa5 i... more The electronic structure of the Pu-based superconductor PuCoGa5 and the Pauli paramagnet UCoGa5 is investigated using photoemission spectroscopy. The photoemission data of PuCoGa5 reveal features at the Fermi energy EF and about 1-1.5 eV below EF indicative of itinerant and localized f-electrons, respectively. Angle-resolved spectra of UCoGa5 show two peaks at similar energies that are highly dispersive, providing evidence for itinerant character of the f-electrons in this material. A comparison of the PuCoGa5 and UCoGa5 data to the spectra of α-Pu and δ-Pu serves to place PuCoGa5 within the context of the more general electronic structure problem in elemental Pu.
The 5f electronic states in elemental Pu and Pu compounds exhibit elements of both itinerant and ... more The 5f electronic states in elemental Pu and Pu compounds exhibit elements of both itinerant and localized behavior. Several first-principles calculations have been presented to describe this balance, differing in the manner in which electron correlation is included in the calculation. This paper describes a calculations performed with the Mixed Level Model (MLM), presenting calculated results for the two Pu compounds, PuRhGa5 and PuCoGa5. The MLM results are compared with other calculations and the differences discussed.
The Chemistry of the Actinide and Transactinide Elements
Page 1. CHAPTER TWENTY ONE 5f‐ELECTRON PHENOMENA IN THE METALLIC STATE AJ Arko, John J. Joyce, an... more Page 1. CHAPTER TWENTY ONE 5f‐ELECTRON PHENOMENA IN THE METALLIC STATE AJ Arko, John J. Joyce, and Ladia Havela 21.1 INTRODUCTION In this chapter, the properties of actinides in the metallic state will be ...
Single crystal antiferromagnetic USb2 was studied at 15K by angle-resolved photoemission in the p... more Single crystal antiferromagnetic USb2 was studied at 15K by angle-resolved photoemission in the photon energy range between 20 eV and 110 eV. The overall energy resolution for lowest energy range was 20 meV, and the momentum resolution was 0.09A-1. The sharp photoemission peak (FWHM 30-50 meV) near the Fermi edge (EF) and Laue patterns confirmed the high quality of the
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Papers by John Joyce