Research Article

Coherent band excitations in CePd3: A comparison of neutron scattering and ab initio theory

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Science  12 Jan 2018:
Vol. 359, Issue 6372, pp. 186-191
DOI: 10.1126/science.aan0593
  • Fig. 1 Electronic spectral function of CePd3 calculated using DFT+DMFT.

    (A) At 100 K, the calculations show the presence of well-defined quasiparticle bands that cross the Fermi energy–producing small electron pockets close to the center of the Brillouin zone (Γ) and the (Embedded Image) zone boundary (R). Flat unoccupied bands near 50 meV are seen at the X point (Embedded Image) and the M point (Embedded Image). (B) At 400 K, the spectral weight close to the Fermi energy is largely incoherent.

  • Fig. 2 Dynamic magnetic susceptibility of CePd3.

    (A to C) Calculations using DFT+DMFT at 100 K compared to (D to F) inelastic neutron scattering on ARCS measured at 5 K. The results are shown as [H0L]/[0KL] planes at constant energy transfers of 35 meV [(A), (B), (D), and (E)] and 55 meV [(C) and (F)], with L = 1 [(A) and (D)] and Embedded Image [(B), (C), (E), and (F)]. In both the calculations and the measurements, the results are averaged over a range of ±5 meV in ω and ±0.2 in L. The intensity is in arbitrary units, with the calculations and the measurements normalized by a single scale factor. No backgrounds have been subtracted from the ARCS data. Black pixels represent regions of reciprocal space that were not measured.

  • Fig. 3 Energy dependence of the dynamic magnetic susceptibility of CePd3.

    (A and B) Merlin data measured at 5 K and (C and D) DFT+DMFT calculations at 100 K, represented by a L-ω slice at H = 1.5 ± 0.25, [(A) and (C)] K = 0.00 ± 0.25, and [(B) and (D)] K = 0.50 ± 0.25.

  • Fig. 4 Energy dependence of the scattering law of CePd3.

    Measurements at 5 K are shown at the Γ (1.00 ± 0.25, 1.00 ± 0.25, 0.00 ± 0.25), X (1.00 ± 0.25, 1.00 ± 0.25, 0.50 ± 0.25), M (1.50 ± 0.25, 0.00 ± 0.25, 0.50 ± 0.25), and R (1.50 ± 0.25, 0.50 ± 0.25, 0.50 ± 0.25) points in the Brillouin zone. The open circles, closed black circles, and closed blue circles are measurements on Merlin with incident energies of 30, 60, and 120 meV, respectively. The solid black lines show the estimated phonon scattering based on a fit to three Gaussians. The energies of the phonon peaks are in good agreement with previous measurements of the CePd3 phonons (32). The red lines are the result of the DFT+DMFT calculations at 100 K after adjusting a single overall scale factor.

  • Fig. 5 Comparison of experiment and calculations of S(Q,ω) on an absolute scale.

    (Top) Left to right, the DFT+DMFT calculations at 100 K in the form of a L-ω slice along Γ → X at H = 1.00 ± 0.25, K= 1.00 ± 0.25; X → M at H = 1.50 ± 0.25, K = 0.00 ± 0.25; and M → R directions at H = 1.50 ± 0.25, K = 0.50 ± 0.25. Three white dashed lines, labeled I, II, and III, show the direction and position in energy of the 1D constant energy cuts at energies of (A to C) 60 ± 5 meV, (D to F) 45.0 ± 2.5 meV, and (G to I) 25.0 ± 2.5 meV, respectively. The inelastic neutron scattering data were measured on Merlin at T = 5 K and integrated in the same energy and H, K range as in the upper three panels. The error bars are derived using Poisson statistics. The data were fit to 1D cuts of the DFT+DMFT calculations, with a single scale factor and quadratic backgrounds as the only adjustable parameters. The fitted backgrounds have been subtracted from the data, so the points represent the estimated magnetic scattering and the lines represent the theoretical calculations. The data and fits without the background subtraction are shown in (30).

  • Fig. 6 Temperature dependence of the dynamic magnetic susceptibility of CePd3.

    (A) The open (closed) circles were measured on the Maps spectrometer at 6 K (300 K) using a fixed sample geometry [see (20) for more details] at the energy transfer of 60 ± 10 meV and K = 0.50 ± 0.25, with backgrounds subtracted using the same method as in Fig. 5. The inset shows how H varies as a function of L. The lines are the results of DFT+DMFT calculations performed at 100 K and 400 K, including the H(L) dependence, and scaled with the same normalization factor for both temperatures. (B and C) Calculations using DFT+DMFT at (B) 100 K and (C) 400 K of χ′′(Q,ω) (black lines), i.e., with corrections due to particle-hole interactions, and Embedded Image (blue lines), without the corrections. The red lines show the calculated Embedded Image at 100 K and 400 K after scaling by factors of 6.5 and 7.5, respectively.

Supplementary Materials

  • Coherent band excitations in CePd3: A comparison of neutron scattering and ab initio theory

    Eugene A. Goremychkin, Hyowon Park, Raymond Osborn, Stephan Rosenkranz, John-Paul Castellan, Victor R. Fanelli, Andrew D. Christianson, Matthew B. Stone, Eric D. Bauer, Kenneth J. McClellan, Darrin D. Byler, Jon M. Lawrence

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Supplementary Text
    • Figs. S1 to S10
    • References

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