Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe

Simon A.J. Kimber; Jiayong Zhang; Charles H. Liang; Gian G. Guzmán-Verri; Peter B. Littlewood; Yongqiang Cheng; Douglas L. Abernathy; Jessica M. Hudspeth; Zhong Zhen Luo; Mercouri G. Kanatzidis; Tapan Chatterji; Anibal J. Ramirez-Cuesta; Simon J.L. Billinge

doi:10.1038/s41563-023-01483-7

Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe

Simon A.J. Kimber, Jiayong Zhang, Charles H. Liang, Gian G. Guzmán-Verri, Peter B. Littlewood, Yongqiang Cheng, Douglas L. Abernathy, Jessica M. Hudspeth, Zhong Zhen Luo, Mercouri G. Kanatzidis, Tapan Chatterji, Anibal J. Ramirez-Cuesta, Simon J.L. Billinge

Research output: Contribution to journal › Article › peer-review

23 Scopus citations

Abstract

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 applications¹. 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 interactions⁶. 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.

Original language	English
Pages (from-to)	311-315
Number of pages	5
Journal	Nature Materials
Volume	22
Issue number	3
DOIs	https://doi.org/10.1038/s41563-023-01483-7
State	Published - Mar 2023

Funding

We thank the European Synchrotron Radiation Facility for the provision of beamline time on ID15B and ID31. This research used resources at the Spallation Neutron Source, a US Department of Energy (DOE), Office of Science User Facility, operated by the Oak Ridge National Laboratory. The computing and software resources were made available through the VirtuES and the ICEMAN projects, funded by the Laboratory Directed Research and Development program (LDRDs 7739, 8237,10447) and Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the DOE under Contract DE-AC05-00OR22725. We thank A. Hill, R. Mills and G. Ganroth for assistance, and A. Tennant and R. Ibberson for supporting a 2017 workshop on Advanced Fourier Methods at the Shull Wollan Center. We thank T. Egami, A. Fitch, P. Senet and M. Wuttig for useful discussions. S.J.L.B. acknowledges support from the US DOE, Office of Science, Office of Basic Energy Sciences, under contract no. DE- SC0012704. C.H.L. acknowledges support from NSF GRFP DGE-1746045. G.G.G.-V. acknowledges support from the Vice-Rector for Research at the University of Costa Rica (project no. 816-C1-601). Work at Argonne (P.B.L.) is supported by the US DOE, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering, under contract no. DE-AC02-06CH11357. At Northwestern University (M.G.K.), work on thermoelectric materials is primarily supported by the US DOE, Office of Science, Office of Basic Energy Sciences, under award no. DE-SC0014520. This work was supported by the Programme of Investments for the Future, an ISITE-BFC project (contract no. ANR-15-IDEX-0003) (S.A.J.K.). We thank the European Synchrotron Radiation Facility for the provision of beamline time on ID15B and ID31. This research used resources at the Spallation Neutron Source, a US Department of Energy (DOE), Office of Science User Facility, operated by the Oak Ridge National Laboratory. The computing and software resources were made available through the VirtuES and the ICEMAN projects, funded by the Laboratory Directed Research and Development program (LDRDs 7739, 8237,10447) and Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the DOE under Contract DE-AC05-00OR22725. We thank A. Hill, R. Mills and G. Ganroth for assistance, and A. Tennant and R. Ibberson for supporting a 2017 workshop on Advanced Fourier Methods at the Shull Wollan Center. We thank T. Egami, A. Fitch, P. Senet and M. Wuttig for useful discussions. S.J.L.B. acknowledges support from the US DOE, Office of Science, Office of Basic Energy Sciences, under contract no. DE- SC0012704. C.H.L. acknowledges support from NSF GRFP DGE-1746045. G.G.G.-V. acknowledges support from the Vice-Rector for Research at the University of Costa Rica (project no. 816-C1-601). Work at Argonne (P.B.L.) is supported by the US DOE, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering, under contract no. DE-AC02-06CH11357. At Northwestern University (M.G.K.), work on thermoelectric materials is primarily supported by the US DOE, Office of Science, Office of Basic Energy Sciences, under award no. DE-SC0014520. This work was supported by the Programme of Investments for the Future, an ISITE-BFC project (contract no. ANR-15-IDEX-0003) (S.A.J.K.).

Funders	Funder number
Compute and Data Environment for Science
National Science Foundation	DGE-1746045
U.S. Department of Energy	DE-AC05-00OR22725
Office of Science
Basic Energy Sciences	DE- SC0012704
Oak Ridge National Laboratory
Laboratory Directed Research and Development	LDRDs 7739, 8237,10447
Division of Materials Sciences and Engineering	ANR-15-IDEX-0003, DE-AC02-06CH11357, DE-SC0014520
Universidad de Costa Rica	816-C1-601

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Kimber, S. A. J., Zhang, J., Liang, C. H., Guzmán-Verri, G. G., Littlewood, P. B., Cheng, Y., Abernathy, D. L., Hudspeth, J. M., Luo, Z. Z., Kanatzidis, M. G., Chatterji, T., Ramirez-Cuesta, A. J., & Billinge, S. J. L. (2023). Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe. Nature Materials, 22(3), 311-315. https://doi.org/10.1038/s41563-023-01483-7

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title = "Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe",

abstract = "Cubic energy materials such as thermoelectrics or hybrid perovskite materials are often understood to be highly disordered1,2. In GeTe and related IV–VI compounds, this is thought to provide the low thermal conductivities needed for thermoelectric applications1. 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 interpretations3–5, 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 interactions6. By accessing time-dependent atomic correlations in energy materials, we resolve the long-standing disagreement between local and average structure probes1,7–9 and show that spontaneous anisotropy is ubiquitous in cubic IV–VI materials.",

author = "Kimber, {Simon A.J.} and Jiayong Zhang and Liang, {Charles H.} and Guzm{\'a}n-Verri, {Gian G.} and Littlewood, {Peter B.} and Yongqiang Cheng and Abernathy, {Douglas L.} and Hudspeth, {Jessica M.} and Luo, {Zhong Zhen} and Kanatzidis, {Mercouri G.} and Tapan Chatterji and Ramirez-Cuesta, {Anibal J.} and Billinge, {Simon J.L.}",

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doi = "10.1038/s41563-023-01483-7",

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AU - Kimber, Simon A.J.

AU - Zhang, Jiayong

AU - Liang, Charles H.

AU - Guzmán-Verri, Gian G.

AU - Littlewood, Peter B.

AU - Cheng, Yongqiang

AU - Abernathy, Douglas L.

AU - Hudspeth, Jessica M.

AU - Luo, Zhong Zhen

AU - Kanatzidis, Mercouri G.

AU - Chatterji, Tapan

AU - Ramirez-Cuesta, Anibal J.

AU - Billinge, Simon J.L.

PY - 2023/3

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N2 - Cubic energy materials such as thermoelectrics or hybrid perovskite materials are often understood to be highly disordered1,2. In GeTe and related IV–VI compounds, this is thought to provide the low thermal conductivities needed for thermoelectric applications1. 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 interpretations3–5, 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 interactions6. By accessing time-dependent atomic correlations in energy materials, we resolve the long-standing disagreement between local and average structure probes1,7–9 and show that spontaneous anisotropy is ubiquitous in cubic IV–VI materials.

AB - Cubic energy materials such as thermoelectrics or hybrid perovskite materials are often understood to be highly disordered1,2. In GeTe and related IV–VI compounds, this is thought to provide the low thermal conductivities needed for thermoelectric applications1. 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 interpretations3–5, 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 interactions6. By accessing time-dependent atomic correlations in energy materials, we resolve the long-standing disagreement between local and average structure probes1,7–9 and show that spontaneous anisotropy is ubiquitous in cubic IV–VI materials.

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Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe

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