Inelastic neutron scattering on (Pr, La)Ni2 and (Pr, Y)Ni2

Mühle, E.; Goremychkin, E. A.; Natkaniec, I.

doi:10.1016/0304-8853(89)90230-8

Cited by 9 publications

(4 citation statements)

References 22 publications

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“…Several studies have proposed the formation of a VBS in other materials, considering an interplay of optical phonons with CEF excitations as in CeAl 2 . For instance, consistent with this mechanism evidence for a VBS in polycrystalline PrNi 2 vanishes as the optical phonon levels shift to lower energies under doping 27 . Putative evidence for vibronic states was also reported in cubic Ce 3 Pt 23 Si 11 28 as well as the tetragonal systems CePd 2 Al 2 10,29 and CeCuAl 3 11 .…”

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confidence: 53%

“…For instance, formation of a vibronic bound state (VBS) between phonons and CEF excitations has been reported in normalCnormalenormalAnormall2 (19–22). Similar VBSs have also been proposed to exist in normalPnormalrnormalNnormali2 (23), normalCnormale3normalPnormalt23normalSnormali11 (24), normalCnormalenormalPnormald2normalAnormall2 (13, 25), and normalCnormalenormalCnormalunormalAnormall3 (14) as well as rare-earth doped cuprates (26) and geometrically frustrated oxides (8, 15, 27). However, as the phonon density of states must be large, it is generally believed that the VBS may be formed only with weakly dispersive optical phonons.…”

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confidence: 62%

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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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confidence: 53%

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confidence: 62%

Magnetoelastic hybrid excitations in CeAuAl ₃

Čermák

Schneidewind

Liu

et al. 2019

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

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“…Representing one of the first examples, seminal studies reported a vibronic bound state (VBS) between phonons and CEF excitations in CeAl 2 . [ 75–78 ] Similar VBSs have also been proposed for PrNi 2 , [ 79 ] Ce 3 Pt 23 Si 11 , [ 80 ] and CePd 2 Al 2 . [ 81,82 ] In contrast, an anticrossing, representing a different magneto‐elastic coupling, has been suggested between acoustic phonons and CEF excitations in Pr and PrAl 2 under an applied magnetic field as well as in the magnetically ordered state of VO 4 .…”

Section: Magneto‐elastic Coupling In Cecualmentioning

confidence: 78%

High‐Pressure Studies of Correlated Electron Systems

Jorba

Regnat

Tong

et al. 2022

Physica Status Solidi (b)

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Tuning the electronic properties of transition‐metal and rare‐earth compounds by virtue of changes of the crystallographic lattice constants offers controlled access to new forms of order. The development of tungsten carbide (WC) and moissanite Bridgman cells conceived for studies of the electrical resistivity up to 10 GPa, as well as bespoke diamond anvil cells (DACs) developed for neutron depolarization studies up to 20 GPa is reviewed. For the DACs, the applied pressure changes as a function of temperature in quantitative agreement with the thermal expansion of the pressure cell. A setup is described that is based on focusing neutron guides for measurements of the depolarization of a neutron beam by samples in a DAC. The technical progress is illustrated in terms of three examples. Measurements of the resistivity and neutron depolarization provide evidence of ferromagnetic order in SrRuO3 up to 14 GPa close to a putative quantum phase transition. Combining hydrostatic, uniaxial, and quasi‐hydrostatic pressure, the emergence of incipient superconductivity in CrB2 is observed. The temperature dependence of the electrical resistivity in CeCuAl3 is consistent with emergent Kondo correlations and an enhanced coupling of magneto‐elastic excitations with the conduction electrons at low and intermediate temperatures, respectively.

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“…It was shown, that this approach cannot explain the magnetic excitation spectra measured in several compounds, e.g. in pyrochlores Tb 2 Ti 2 O 7 1 , Ho 2 Ti 2 O 7 2 , intermetallics CeAl 2 3 , PrNi 2 4 , CePd 2 Al 2 5 , CeCuAl 3 6 and recently in CeAuAl 3 7 . The Ce-based intermetallics have a very prominent position with a relatively small number of expected CEF excitations.…”

Section: Introductionmentioning

confidence: 99%

Lattice dynamics in CePd2Al2 and LaPd2Al2

Doležal

Cejpek

Tsutsui

et al. 2021

Sci Rep

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The interaction between phonons and 4f electrons, which is forming a new quantum state (quasi-bound state) beyond Born-Oppenheimer approximation, is very prominent and lattice dynamics plays here a key role. There is only a small number of compounds in which the experimental observation suggest such a scenario. One of these compounds is CePd2Al2. Here the study of phonon dispersion curves of (Ce,La)Pd2Al2 at 1.5, 7.5, 80 and 300 K is presented. The inelastic X-ray scattering technique was used for mapping the phonon modes at X and Z points as well as in Λ and Δ directions, where the symmetry analysis of phonon modes was performed. The measured spectra are compared with the theoretical calculation, showing very good agreement. The measurements were performed in several Brillouin zones allowing the reconstruction of phonon dispersion curves. The results are discussed with respect to the magneto-elastic interaction and are compared with other cerium compounds. The phonon mode symmetry A1g was found to be unaffected by the interaction, which is in contrast to previous assumptions.

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Inelastic neutron scattering on (Pr, La)Ni2 and (Pr, Y)Ni2

Cited by 9 publications

References 22 publications

Magnetoelastic hybrid excitations in CeAuAl ₃

Magnetoelastic hybrid excitations in CeAuAl ₃

High‐Pressure Studies of Correlated Electron Systems

Lattice dynamics in CePd2Al2 and LaPd2Al2

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Inelastic neutron scattering on (Pr, La)Ni2 and (Pr, Y)Ni2

Cited by 9 publications

References 22 publications

Magnetoelastic hybrid excitations in CeAuAl 3

Magnetoelastic hybrid excitations in CeAuAl 3

High‐Pressure Studies of Correlated Electron Systems

Lattice dynamics in CePd2Al2 and LaPd2Al2

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Product

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Magnetoelastic hybrid excitations in CeAuAl ₃

Magnetoelastic hybrid excitations in CeAuAl ₃