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Impact of temperature and mode polarization on the acoustic phonon range in complex crystalline phases: A case study on intermetallic clathrates

Turner, S. R.; Pailhès, S.; Bourdarot, F.; Ollivier, J.; Raymond, S.; Keller, T.; Sidis, Y.; Castellan, J.-P.; Lory, P.-F.; Euchner, H.; Baitinger, M.; Grin, Yu.; Schober, H.; Boissieu, M. de; Giordano, V. M.

Abstract (englisch):

The low and weakly temperature-varying lattice thermal conductivity, κL (T), in crystals with a complex unit
cell such as type-I clathrates is assumed to originate from a reduced momentum and energy space available for
propagative lattice vibrations, which is caused by the occurrence of low-energy optical phonon modes. In the
context of ab initio self-consistent phonon (SCP) theory, it has been shown that the cubic and quartic anharmonic
interactions result in a temperature-induced energy renormalization of these low-lying optical branches which
contributes to the anomalous behavior of κL (T) in structurally ordered type-I clathrates [T. Tadano and S.
Tsuneyuki, Phys. Rev. Lett. 120, 105901 (2018)]. By means of inelastic neutron scattering, we provide evidence
for this energy renormalization in temperature, which has been resolved for transversely and longitudinally
polarized phonons in the single crystal type-I clathrate Ba7.81Ge40.67Au5.33. By mapping the neutron intensity
in the momentum space, we demonstrate the coherent character of the low-lying optical phonons. The overall
phonon spectrum and dynamical structure factors are satisfactorily reproduced by ab initio harmonic calculations
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Verlagsausgabe §
DOI: 10.5445/IR/1000137678
Veröffentlicht am 21.09.2021
DOI: 10.1103/PhysRevResearch.3.013021
Zitationen: 1
Zitationen: 2
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Festkörperphysik (IFP)
Institut für Quantenmaterialien und -technologien (IQMT)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 01.2021
Sprache Englisch
Identifikator ISSN: 2643-1564
KITopen-ID: 1000137678
HGF-Programm 47.11.02 (POF IV, LK 01) Emergent Quantum Phenomena
Erschienen in Physical review research
Verlag American Physical Society (APS)
Band 3
Heft 1
Seiten Article no: 013021
Vorab online veröffentlicht am 08.01.2021
Nachgewiesen in Scopus
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