Theoretical Aspects of the Charge Density Wave in Uranium

Fast, Lars; Eriksson, Olle; Johansson, Börje; Wills, J. M.; Straub, Galen K.; Roeder, H.; Nordström, Lars

doi:10.1103/physrevlett.81.2978

Cited by 71 publications

(99 citation statements)

References 18 publications

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“…Neutron diffraction experiments by Marmeggi et al (1990) show there are three separate CDWs, one at 43 K (α 1 ), one at 37 K (α 2 ), and one at 22 K (α 3 ), where α 1 and α 2 are incommensurate with the lattice and α 3 is commensurate. First-principles calculations by Fast et al (1998) show the strong nesting of the narrow 5f bands in the Fermi surface for the α 1 phase Given the fact that CDWs form in α-U, a delocalized actinide metal with a low-symmetry orthorhombic crystal structure, one may reasonably ask whether CDW(s) form in orthorhombic α-Np or monoclinic α-Pu. Unpublished research by Butterfield and Moore show no CDW forms in α-Pu to 8 K. Using a liquid-helium specimen holder, an α-Pu sample is cooled in a TEM, where no superlattice reflections are observed in electron diffraction.…”

Section: Charge Density Waves In α-U; In α-Np and α-Pu Also?mentioning

confidence: 99%

“…In order to counter the lack of experimental data, we are progressively recording the various core d → valence f transitions of the actinides using electron energy-loss spectroscopy 1 Examples: Gupta and Loucks, 1969;Skriver et al, 1978;Skriver, 1985;Solovyev et al, 1991;Söderlind et al, 1995;van der Laan and Thole, 1996;Penicaud, 1997;Fast et al, 1998;Söderlind, 1998;Eriksson et al, 1999;Savrasov and Kotliar, 2000;Savrasov et al, 2001;Dai et al, 2003;Kutepov and Kutepova, 2003;Söderlind and Sadigh, 2004;Wills et al, 2004;Shick et al, 2005;Pourovskii et al, 2005;Moore et al, 2006a;Shick et al, 2006;Shim et al, 2007;Svane et al, 2007.…”

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confidence: 99%

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Nature of the5fstates in actinide metals

2009

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Actinide elements produce a plethora of interesting physical behaviors due to the 5f states. This review compiles and analyzes progress in understanding of the electronic and magnetic structure of the 5f states in actinide metals. Particular interest is given to electron energy-loss spectroscopy and many-electron atomic spectral calculations, since there is now an appreciable library of core d → valence f transitions for Th, U, Np, Pu, Am, and Cm. These results are interwoven and discussed against published experimental data, such as x-ray photoemission and absorption spectroscopy, transport measurements, and electron, x-ray, and neutron diffraction, as well as theoretical results, such as density-functional theory and dynamical mean-field theory.

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Section: Charge Density Waves In α-U; In α-Np and α-Pu Also?mentioning

confidence: 99%

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confidence: 99%

Nature of the5fstates in actinide metals

2009

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“…The present authors have participated 11,12,[14][15][16][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] in this theoretical advancement using a first-principles relativistic, full-potential technique implemented using the linear muffin-tin orbitals method. A large percentage of these results have been on elemental actinides.…”

Section: Introductionmentioning

confidence: 99%

Spin-orbit coupling in the actinide elements: A critical evaluation of theoretical equilibrium volumes

et al. 2000

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In a recent paper by Jones et al.1 , it is argued, based on FP-LAPW band-structure calculations, that previous calculations of ground-state properties for actinides, using the FP-LMTO method implemented by J.M. Wills 2 , are in error. We demonstrate in this paper that the conclusions of Jones et. al.1 are unfounded. Calculations using the FP-LMTO method are compared with calculations performed with the FP-LAPW method and, in contradiction to statements by Jones et. al., they agree very well. The limitation of the present implementation of the spin-orbit coupling is discussed, where especially the 6p states pose a difficulty. The observed discrepancy (0-10%) between the FP-LMTO calculations and the recent FP-LAPW calculation of Jones et al. is shown to be due to the choice of muffin-tin radius in the calculations. We argue that the choice of a constant muffin-tin radius, common for all calculated volumes, is less satisfactory compared to the choice of a muffin-tin radius that scales with the volume, especially when a large volume interval and open packed structures are considered. The conclusion of Jones et al. that α-Pu has partially delocalized 5f electrons is argued to be erroneous.

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“…Substantial Fermi-surface nesting for a 3D material is extremely rare. One example is found in α-uranium 23 , where it gives rise to a charge density wave, rather than to a spin density wave. For the rare-earth elements, including Tb and Dy, a webbing feature at the zone boundary specific to their hexagonal crystal structure may provide such a special case 19 .…”

Section: Nature Physics Doi: 101038/nphys3238mentioning

confidence: 99%

Modulated magnetism in PrPtAl

et al. 2015

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The transition between paramagnetism and ferromagnetism is the paradigm for a continuous phase transition at finite temperature. When such a transition is tuned to zero temperature in clean materials, the growth of low-energy zero-point fluctuations potentially drives an array of phenomena, including the formation of novel states such as nonconventional superconductivity. Experimentally, the growth of the fluctuations, however, is curtailed and the transition becomes discontinuous as its temperature is reduced. This is understood to arise from non-analytic corrections to the free energy that always occur 1 . In a recent theory 2,3 , changes of the excitation spectrum are self-consistently considered alongside the ground state. This analysis reveals that a transition to a new state may be an alternative outcome. As the excitation spectrum (the 'disorder') is pivotal to promoting the new 'order' this mechanism is referred to as 'order by disorder'. Here, we report the discovery of modulated order in PrPtAl, consistent with complex spirals, at the boundary between paramagnetism and ferromagnetism, giving the first clear experimental realization of such a state.In our theoretical model, deformations of the Fermi surface in the modulated state enlarge the phase space available for low-energy particle-hole fluctuations and this self-consistently lowers the free energy relative to a uniform ferromagnetic state. Although previous theory predicting spiral formation 4,5 based on this mechanism has considered isotropic magnets, easy-plane systems are better candidate materials, as a hard magnetic axis provides a natural orientation for the spiral wavevector and suppresses 'unwanted' moment fluctuations along the spiral direction. The anisotropy can be introduced with local moments 6 , although the theoretical description close to a ferromagnetic quantum critical point 7 has only recently been extended to include the coupling of these moments to the conduction electrons 8 . Here we describe our findings for PrPtAl. This material is close to being an easy-plane ferromagnet, but has an additional magnetic anisotropy between the two easy axes in the plane. The electronic levels of the praseodymium 4f 2 Pr 3+ ions are split in the crystal environment (PrPtAl has an orthorhombic TiNiSn structure) into nine non-magnetic singlet states. Inelastic neutron studies 9 reveal clear crystal field excitations between these. Choosing a system with only singlets simplifies the theory considerably, avoiding Kondo lattice physics, while still introducing magnetic anisotropy.As there are no preformed moments, ferromagnetic order is achieved by mixing singlets via an inter-site exchange interaction 10 , a process referred to as induced-moment magnetism. Our theoretical approach to analysing the magnetic interactions that bring about magnetic order in PrPtAl differs from the standard treatment 11 by keeping the full frequency dependence of the fermion-mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. This is the key element for a descr...

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Theoretical Aspects of the Charge Density Wave in Uranium

Cited by 71 publications

References 18 publications

Nature of the5fstates in actinide metals

Nature of the5fstates in actinide metals

Spin-orbit coupling in the actinide elements: A critical evaluation of theoretical equilibrium volumes

Modulated magnetism in PrPtAl

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