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@ARTICLE{ermk:862499,
      author       = {Čermák, Petr and Schneidewind, Astrid and Liu, Benqiong
                      and Koza, Michael Marek and Franz, Christian and Schönmann,
                      Rudolf and Sobolev, Oleg and Pfleiderer, Christian},
      title        = {{M}agnetoelastic hybrid excitations in {C}e{A}u{A}l 3},
      journal      = {Proceedings of the National Academy of Sciences of the
                      United States of America},
      volume       = {116},
      number       = {14},
      issn         = {1091-6490},
      address      = {Washington, DC},
      publisher    = {National Acad. of Sciences},
      reportid     = {FZJ-2019-02805},
      pages        = {6695 - 6700},
      year         = {2019},
      abstract     = {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 of CeAuAl3,
                      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 in CeAuAl3 arises 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 of
                      CeAuAl3 identifies a tractable point of reference in the
                      search for magneto-elastic functionalities and
                      instabilities.},
      cin          = {JCNS-FRM-II / JCNS-2 / MLZ},
      ddc          = {500},
      cid          = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-2-20110106 / I:(DE-588b)4597118-3},
      pnm          = {6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
                      Neutron Research (JCNS) (POF3-623)},
      pid          = {G:(DE-HGF)POF3-6G15 / G:(DE-HGF)POF3-6G4},
      experiment   = {EXP:(DE-MLZ)PANDA-20140101 / EXP:(DE-MLZ)PUMA-20140101},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:30894488},
      UT           = {WOS:000463069900036},
      doi          = {10.1073/pnas.1819664116},
      url          = {https://juser.fz-juelich.de/record/862499},
}