Coupled quadrupole-phonon excitations: Inelastic Neutron scattering on van vleck paramagnet PrNi5

Аксенов, В. Л.; Goremychkin, E. A.; Mühle, E.; Frauenheim, Thomas; Bührer, W.

doi:10.1016/0378-4363(83)90398-4

Cited by 13 publications

(9 citation statements)

References 4 publications

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“…(60) and SI Appendix ). Following considerations first reported for normalPnormalrnormalNnormali5 (39) the Hamiltonian of the ME coupling, HnormalMnormalEI, describes the direct coupling between the deformations of the lattice and the 4f shell. In a group theoretical analysis (64) the energy of the coupled phonon–CEF excitation, which is mediated by quadrupolar interactions, is given byωq±2=E2+ω022±()E2−ω0222+16α2Eω02gnormalAnormalC,where ωq± represents the energies of the two anticrossing excitations; ω0 is the phonon energy which depends on boldk, E is the nondispersive energy of the CEF level, and gnormalAnormalC is an effective coupling constant related to the renormalization of the elastic constant ( SI...…”

Section: Discussionmentioning

confidence: 99%

“…In comparison, a generic anticrossing in zero magnetic field between phonons and CEFs that is mediated by quadrupolar interactions in a paramagnetic state has been predicted only theoretically. Putative evidence for the latter may have been observed in the insulators normalPnormalrnormalAnormallnormalO3 (37) and normalTnormalbnormalVnormalO4 (38); in the rare-earth (RE) compound normalPnormalrnormalNnormali5 the evidence is indirect (39, 40).…”

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confidence: 99%

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Magnetoelastic hybrid excitations in CeAuAl ₃

Čermák

Schneidewind

Liu

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Nearly a century of research has established the Born–Oppenheimer approximation as a cornerstone of condensed-matter systems, stating that the motion of the atomic nuclei and electrons may be treated separately. Interactions beyond the Born–Oppenheimer approximation are at the heart of magneto-elastic functionalities and instabilities. We report comprehensive neutron spectroscopy and ab initio phonon calculations of the coupling between phonons, CEF-split localized 4f electron states, and conduction electrons in the paramagnetic regime ofCeAuAl3, an archetypal Kondo lattice compound. We identify two distinct magneto-elastic hybrid excitations that form even though all coupling constants are small. First, we find a CEF–phonon bound state reminiscent of the vibronic bound state (VBS) observed in other materials. However, in contrast to an abundance of optical phonons, so far believed to be essential for a VBS, the VBS inCeAuAl3arises from a comparatively low density of states of acoustic phonons. Second, we find a pronounced anticrossing of the CEF excitations with acoustic phonons at zero magnetic field not observed before. Remarkably, both magneto-elastic excitations are well developed despite considerable damping of the CEFs that arises dominantly by the conduction electrons. Taking together the weak coupling with the simultaneous existence of a distinct VBS and anticrossing in the same material in the presence of damping suggests strongly that similarly well-developed magneto-elastic hybrid excitations must be abundant in a wide range of materials. In turn, our study of the excitation spectra ofCeAuAl3identifies a tractable point of reference in the search for magneto-elastic functionalities and instabilities.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Magnetoelastic hybrid excitations in CeAuAl ₃

Čermák

Schneidewind

Liu

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…Several studies have reported putative evidence of an anticrossing of acoustic phonons and quadrupole excitations, e.g., in PrAlO 3 15 , TbVO 4 16 , TmVO 4 17 . In contrast, in intermetallic compounds an anticrossing could only be inferred indirectly as reported for PrNi 5 18 . When the magnetoelastic coupling becomes very strong, a completely different excitation spectrum may be expected resulting in the formation of a bound state between lowlying optical phonons and a crystal field excitation.…”

Section: Introductionmentioning

confidence: 90%

“…As mentioned above, a lot of effort has been devoted to the study of coupled quadrupole-phonon excitations reflecting magnetoelastic interactions. [15][16][17][18] Several theoretical derivations for the mixed-mode excitation dispersion have been reported. Using a diagrammatic method the mixed-mode excitation dispersion may be inferred from the poles of the dynamical susceptibility of the system of RE ions.…”

Section: Coupled Quadrupole-phonon Excitationsmentioning

confidence: 99%

Lattice dynamics and coupled quadrupole-phonon excitations in CeAuAl3

et al. 2018

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We report first principles calculations of the structural parameters and phonon dispersion of the tetragonal non-centrosymmetric heavy fermion compound CeAuAl3. Taking into account weak magnetoelastic interactions of the rare-earth (RE) ions with the spectrum of phonons, we obtain an analytical expression for the hybridization of quadrupole excitations and phonons from the poles of the one-phonon Green-function. In the paramagnetic phase, we predict the formation of mixed modes that may be observed by inelastic neutron scattering. Our results show that magnetoelastic interactions, albeit being moderate, play an important role in CeAuAl3. This suggests that magnetoelastic interactions may be equally important in a wide range of related compounds.

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“…This strong CEFphonon coupling may even yield vibronic bound states. CEFphonon coupling has been observed in CeAuAl 3 , 36,44 Ce 2 O 3 , 35 CeAl 2 , [45][46][47] PrNi 5 , 48 NdBa 2 Cu 3 O 7Àd , 49 and Ho 2 Ti 2 O 7 , 50 among other materials. Conduction electrons may further complicate the picture and alter the relative intensity of hybrid modes.…”

Section: Introductionmentioning

confidence: 91%