E L E C T R O N I C S T R U C T U R E , M A G N E T I S M A N D D Y N A M I C S
S C I E N T I F I C H I G H L I G H T S
1 1 0 H I G H L I G H T S 2 0 2 2 I
thus to enable an interpretation of resonant inelastic X-ray scattering (RIXS).
The ability to resolve two-particle excitations of Kondo lattices with RIXS indeed proved to be a powerful innovation [3]. The data on CePd3, obtained at beamline ID32, showcase how different quasiparticle excitations can be separated and enhanced by the choice of incident energy and polarisation, revealing higher-energy transitions that are not accessible to neutrons. The lattice character of Kondo quasiparticle dynamics, which in CePd3 emerges around 150 K, has an impressive impact on the RIXS signal: as hybridisation gaps open, excitations shift to higher energies and, as a coherent quasiparticle band structure emerges, the RIXS response becomes momentum- dependent (Figure 103).
First principles calculations reveal interesting details of this process, such as the reorganisation of the quasiparticle bands with different orbital symmetries (Figure 102). On the other hand, calculating momentum-dependent
Fig. 103: Emergent Kondo coherence in CePd3. At room temperature (top), the RIXS response is
largely isotropic. The momentum dependence of these spectra at low temperature (bottom)
provides a fingerprint of dispersive Kondo quasiparticle bands.
RIXS in a correlated itinerant system like CePd3 remains an outstanding challenge. At a minimum, the current approach, based on a momentum-independent self- energy, provides a means to qualitatively capture the key characteristics of the experiment.
For many decades, experimental knowledge of Kondo dynamics has been limited to the perspective of bulk or momentum-averaged probes, which disguise the fine structure of the underlying valence fabric. As more systematic investigations on the relevant scales of space and time become available, new fundamental insights into local-itinerant entanglement may be in store.
PRINCIPAL PUBLICATION AND AUTHORS
Kondo quasiparticle dynamics observed by resonant inelastic x-ray scattering, M.C. Rahn (a,b), K. Kummer (c), A. Hariki (d,e), K.-H. Ahn (e,f), J. Kuneš (e), A. Amorese (g,h), J.D. Denlinger (i), D.-H. Lu (j), M. Hashimoto (j), E. Rienks (k), M. Valvidares (l), F. Haslbeck (m,n), D.D. Byler (a), K.J. McClellan (a), E.D. Bauer (a), J.X. Zhu (a), C.H. Booth (o), A.D. Christianson (p), J.M. Lawrence (a,q), F. Ronning (a), M. Janoschek (a,n,r,s), Nat. Commun. 13, 6129 (2022); https:/doi.org/10.1038/s41467-022-33468-6 (a) Los Alamos National Laboratory (USA) (b) Institute for Solid State and Materials Physics, Technical University of Dresden (Germany) (c) ESRF (d) Department of Physics and Electronics, Osaka Prefecture University (Japan) (e) Institute for Solid State Physics, TU Vienna (Austria) (f) Institute of Physics of the CAS, Prague (Czechia) (g) Institute of Physics II, University of Cologne (Germany) (h) Max Planck Institute for Chemical Physics of Solids, Dresden (Germany) (i) Advanced Light Source, Lawrence Berkeley Laboratory (USA) (j) Stanford Synchrotron Radiation Lightsource (USA) (k) Helmholtz Zentrum Berlin, Bessy II (Germany) (l) ALBA Synchrotron Light Source, Barcelona (Spain) (m) Physik-Department, Technische Universität München (Germany) (n) Institute for Advanced Studies, Technische Universität München (Germany) (o) Chemical Sciences Division, Lawrence Berkeley National Laboratory (USA) (p) Oak Ridge National Laboratory (USA) (q) Department of Physics and Astronomy, University of California, Irvine (USA) (r) Laboratory for Neutron and Muon Instrumentation, Paul Scherrer Institute, Villigen (Switzerland) (s) Physik-Institut, Universität Zürich (Switzerland)
REFERENCES
[1] P. Coleman, in PWA90: A Lifetime of Emergence, P. Chandra et al. (Eds.), World Scientific, 187- 213 (2016). [2] E.A. Goremychkin et al., Science 359, 186-191 (2018). [3] J.N. Hancock et al., J. Magn. Magn. Mater. 400, 41-46 (2016).
