Possible Bose-condensate behavior in a quantum phase originating in a collective excitation in the chemically and optically doped Mott-Hubbard system UO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>

Conradson, Steven D.; Durakiewicz, Tomasz; Espinosa-Faller, Francisco J.; An, Yongli; Andersson, David; Bishop, A. R.; Boland, Kevin S.; Bradley, J. A.; Byler, Darrin D.; Clark, David L.; Conradson, Dylan R.; Conradson, Leilani L.; Costello, Alison L.; Hess, Nancy J.; Lander, G. H.; Llobet, Anna; Martucci, Mary B.; León, J.; Nordlund, Dennis; Lezama‐Pacheco, Juan S.; Proffen, Thomas; Rodriguez, George; Schwarz, Daniel E.; Seidler, Gerald T.; Taylor, Antoinette J.; Trugman, S. A.; Tyson, Trevor; Valdez, James A.

doi:10.1103/physrevb.88.115135

Cited by 42 publications

(41 citation statements)

References 141 publications

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“…The spectra derived from the uraninite sample and the sample labelled ‘UO 2 ’ are plotted in Figure , along with spectra for UO 2 , U 3 O 7 , U 3 O 8 and UO 3 taken from the literature (Conradson et al . ). A comparison with published values suggests that the uraninite sample in this study is actually U 3 O 7 , since these two spectra share the most features in common.…”

Section: Resultsmentioning

confidence: 97%

Identification of Uranyl Minerals Using Oxygen K‐Edge X‐Ray Absorption Spectroscopy

Ward

Bowden

Resch

et al. 2015

Geostandard Geoanalytic Res

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Although most of the world's uranium exists as pitchblende or uraninite, this mineral can be weathered to a great variety of secondary uranium minerals, most containing the uranyl cation. Anthropogenic uranium compounds can also react in the environment, leading to spatial–chemical alterations that could be useful for nuclear forensics analyses. Soft X‐ray absorption spectroscopy (XAS) has the advantages of being non‐destructive, element‐specific and sensitive to electronic and physical structure. The soft X‐ray probe can also be focused to a spot size on the order of tens of nanometres, providing chemical information with high spatial resolution. However, before XAS can be applied at high spatial resolution, it is necessary to find spectroscopic signatures for a variety of uranium compounds in the soft X‐ray spectral region. To that end, we collected the near edge X‐ray absorption fine structure (NEXAFS) spectra of a variety of common uranyl‐bearing minerals, including uranyl carbonates, oxyhydroxides, phosphates and silicates. We find that uranyl compounds can be distinguished by class (carbonate, oxyhydroxide, phosphate or silicate) based on their oxygen K‐edge absorption spectra. This work establishes a database of reference spectra for future spatially resolved analyses. We proceed to show scanning X‐ray transmission microscopy (STXM) data from a schoepite particle in the presence of an unknown contaminant.

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Section: Resultsmentioning

confidence: 97%

Identification of Uranyl Minerals Using Oxygen K‐Edge X‐Ray Absorption Spectroscopy

Ward

Bowden

Resch

et al. 2015

Geostandard Geoanalytic Res

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“…The synchronization of this internal reaction throughout the U 4 O 9 -type domain formed by the aggregation of the adventitious O or photoinduced charges then gives the coherence that defines the polaronic Bose-Einstein(-Mott) condensate. We have previously reported the O XAS of UO 2+x that demonstrated a significant enhancement of the widths of the U 5f states in the upper Hubbard band (UHB, the conduction band) that is opposed to the trend of narrower spectral features with increasing charge 29 that we attributed to the mixing of the electronic states and increased dispersion that occurs with a dynamical polaron. 31 We now examine these results in greater detail to show that this increased dispersion specifically reduces the lower boundary of the UHB.…”

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confidence: 65%

“…The noise level of the NIXS causes difficulties in determining the energies of the features, a problem that is ameliorated by taking the derivatives that also finds the energies of the features of interest more accurately. In this case the issue is not the increase in the dispersion and total width of the DOS with doping that has been described previously 29 but more specifically the effects on the gap. The energies of the inflection points of the initial Figure 4.…”

Section: O Xas Of Standards and Uomentioning

confidence: 91%

“…Samples were prepared and NIXS and XAS experiments were performed as previously described, 29,[40][41][42] as were the calculations. 43…”

Section: Experimental and Calculation Methodsmentioning

confidence: 99%

“…This behavior establishes the environment that promotes the dynamical polaron in fluorite structured, chemically or photodoped UO 2(+x) . 29,30 The 2 U(V)  U(IV) + U(VI) disproportionation excitation of these polarons would occur easily via the transfer of O ions between their buckled-apical positions for fluorite and planar-apical positions for layered, triggered by a [111] type acoustic phonon that causes the separation of the (111) U planes to oscillate. The synchronization of this internal reaction throughout the U 4 O 9 -type domain formed by the aggregation of the adventitious O or photoinduced charges then gives the coherence that defines the polaronic Bose-Einstein(-Mott) condensate.…”

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confidence: 99%

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Anomalous dispersion and band gap reduction in UO2+ and its possible coupling to the coherent polaronic quantum state

Conradson

Andersson

Bagus

et al. 2016

Nuclear Instruments and Methods in Physics Research Section B:

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Hypervalent UO 2 , UO 2(+x) formed by both addition of excess O and photoexcitation, exhibits a number of unusual or often unique properties that point to it hosting a polaronic Bose-Einstein(-Mott) condensate. A more thorough analysis of the O x-ray absorption spectra of UO 2 , U 4 O 9 , and U 3 O 7 shows that the anomalous increase in the width of the spectra features assigned to predominantly U 5f and 6d final states that points to increased dispersion of these bands occurs on the low energy side corresponding to the upper edge of the gap bordered by the conduction or upper Hubbard band. The closing of the gap by 1.5 eV is more than twice as much as predicted by calculations, consistent with the dynamical polaron found by structural measurements. In addition to fostering the excitation that is the proposed mechanism for the coherence, the likely mirroring of this effect on the occupied, valence side of the gap below the Fermi level points to increased complexity of the electronic structure that could be associated with the Fermi topology of BEC-BCS crossover and two band superconductivity.

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X-ray absorption spectroscopy study of cobalt mononitride thin films

et al. 2019

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We present a comprehensive study to resolve the debate about the structure of cobalt mononitride (CoN). In contradiction with theoretical predictions, experimentally CoN has been claimed to synthesize in a rock-salt (RS) and in a zincblende (ZB)-type structure under ambient pressure and temperature. Utilizing X-ray absorption near-edge spectroscopy (XANES) at Co and N K-edges and extended X-ray absorption fine structure (EXAFS) at Co K-edge, we investigated the structure of CoN in detail. The presence of a strong pre-edge feature at the Co K-edge and the absence of t 2 feature at the N K-edge indicate towards the tetrahedral coordination that is expected in the ZB-type structure of CoN. Theoretical simulations of XANES spectra unambiguously confirm the ZB-type structure in CoN. Also from EXAFS data, we found that CoN and Co-Co bond distances match well with ZB-CoN. Magnetic properties of CoN were examined using polarized neutron reflectivity and bulk magnetization measurements. It was found that CoN sample exhibits a paramagnetic behaviour as expected in ZB-CoN. Obtained results clearly demonstrate that CoN indeed crystalizes in the ZB-type structure, and the possibility of the RS-type CoN can be ruled out under ambient pressure and temperature. It is anticipated that the information about the structure of CoN can be utilized for its usage in emerging areas such as low-cost catalyst in oxygen and hydrogen evaluation reactions, high capacity anode in ion batteries and in photovoltaic applications.

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Possible Bose-condensate behavior in a quantum phase originating in a collective excitation in the chemically and optically doped Mott-Hubbard system UO2+x

Cited by 42 publications

References 141 publications

Identification of Uranyl Minerals Using Oxygen K‐Edge X‐Ray Absorption Spectroscopy

Identification of Uranyl Minerals Using Oxygen K‐Edge X‐Ray Absorption Spectroscopy

Anomalous dispersion and band gap reduction in UO2+ and its possible coupling to the coherent polaronic quantum state

X-ray absorption spectroscopy study of cobalt mononitride thin films

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