Abstract
Localization of charge carriers in crystalline solids has been the subject of numerous investigations over more than half a century. Materials that show a metal–insulator transition without a structural change are therefore of interest. Mechanisms leading to metal–insulator transition include electron correlation (Mott transition) or disorder (Anderson localization), but a clear distinction is difficult. Here we report on a metal–insulator transition on increasing annealing temperature for a group of crystalline phase-change materials, where the metal–insulator transition is due to strong disorder usually associated only with amorphous solids. With pronounced disorder but weak electron correlation, these phase-change materials form an unparalleled quantum state of matter. Their universal electronic behaviour seems to be at the origin of the remarkable reproducibility of the resistance switching that is crucial to their applications in non-volatile-memory devices. Controlling the degree of disorder in crystalline phase-change materials might enable multilevel resistance states in upcoming storage devices.
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Acknowledgements
We would like to thank F. Evers, A. Kapitulnik, S. Kievelson, T. Geballe, B. Shklovskii and B. Spivak for discussions. Financial support by the Deutsche Forschungsgemeinschaft (Wu243/17), the Seed Funds of the Faculty for Mathematics, Informatics, and the Natural Sciences at RWTH Aachen and the Alexander von Humboldt Foundation (for T.S.) is acknowledged.
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M. Woda and P.M. prepared the samples. Measurements were carried out by M. Woda (high-temperature R(T)), P.M. (X-ray) and H.V. (low-temperature R(T), Hall effect). The custom-designed Hall set-up was developed by C.S. Analysis of the data was carried out by P.J., and the paper was written by T.S. and M. Wuttig, and P.J. composed the Supplementary Information. The project was initiated by M. Wuttig.
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Siegrist, T., Jost, P., Volker, H. et al. Disorder-induced localization in crystalline phase-change materials. Nature Mater 10, 202–208 (2011). https://doi.org/10.1038/nmat2934
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DOI: https://doi.org/10.1038/nmat2934
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