Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe.

Autor: Kimber SAJ; Université Bourgogne Franche-Comté, Université de Bourgogne, Nanosciences Department, ICB-Laboratoire Interdisciplinaire Carnot de Bourgogne, Bâtiment Sciences Mirande, Dijon, France. sajkimber@protonmail.com., Zhang J; Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA., Liang CH; James Franck Institute, University of Chicago, Chicago, IL, USA.; Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA., Guzmán-Verri GG; Centro de Investigación en Ciencia e Ingeniería de Materiales (CICIMA), Universidad de Costa Rica, San José, Costa Rica.; Escuela de Física, Universidad de Costa Rica, San José, Costa Rica., Littlewood PB; James Franck Institute, University of Chicago, Chicago, IL, USA.; Materials Science Division, Argonne National Laboratory, Argonne, IL, USA., Cheng Y; Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA., Abernathy DL; Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA., Hudspeth JM; ESRF, The European Synchrotron, Grenoble, France., Luo ZZ; Department of Chemistry, Northwestern University, Evanston, IL, USA., Kanatzidis MG; Department of Chemistry, Northwestern University, Evanston, IL, USA., Chatterji T; Institut Laue-Langevin, Grenoble, France., Ramirez-Cuesta AJ; Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA. ramirezcueaj@ornl.gov., Billinge SJL; Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA. sb2896@columbia.edu.; Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA. sb2896@columbia.edu.
Jazyk: angličtina
Zdroj: Nature materials [Nat Mater] 2023 Mar; Vol. 22 (3), pp. 311-315. Date of Electronic Publication: 2023 Feb 20.
DOI: 10.1038/s41563-023-01483-7
Abstrakt: Cubic energy materials such as thermoelectrics or hybrid perovskite materials are often understood to be highly disordered 1,2 . In GeTe and related IV-VI compounds, this is thought to provide the low thermal conductivities needed for thermoelectric applications 1 . Since conventional crystallography cannot distinguish between static disorder and atomic motions, we develop the energy-resolved variable-shutter pair distribution function technique. This collects structural snapshots with varying exposure times, on timescales relevant for atomic motions. In disagreement with previous interpretations 3-5 , we find the time-averaged structure of GeTe to be crystalline at all temperatures, but with anisotropic anharmonic dynamics at higher temperatures that resemble static disorder at fast shutter speeds, with correlated ferroelectric fluctuations along the <100> c direction. We show that this anisotropy naturally emerges from a Ginzburg-Landau model that couples polarization fluctuations through long-range elastic interactions 6 . By accessing time-dependent atomic correlations in energy materials, we resolve the long-standing disagreement between local and average structure probes 1,7-9 and show that spontaneous anisotropy is ubiquitous in cubic IV-VI materials.
(© 2023. The Author(s).)
Databáze: MEDLINE
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