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arXiv · 2301.05773

Nanoscale Sn off-centering behind low thermal conductivity in SnSe thermoelectric

E. S. Bozin·H. Xie·A. M. M. Abeykoon·S. M. Everett·M. G. Tucker·M. G. Kanatzidis·S. J. L. Billinge
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Abstract

The local atomic structure of SnSe was characterized across its orthorhmbic-to-orthorhombic structural phase transition using x-ray pair distribution function analysis. Substantial Sn off-centering distortions persist in the high symmetry high temperature phase, with symmetry different from that of ordered distortions below the transition. The analysis implies that the transition is neither order-disorder nor displacive, but rather a complex crossover where the character of coupling changes from 3D-like at low temperature to 2D-like at high temperature. Robust ferro-coupled SnSe intra-layer distortions suggest a ferroelectric-like instability as the driving force. Complex local Sn off-centering is integral to the ultra-low lattice thermal conductivity mechanism in SnSe.

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E. S. Bozin, H. Xie, A. M. M. Abeykoon, S. M. Everett, M. G. Tucker, M. G. Kanatzidis, S. J. L. Billinge. 2023-01-13. Nanoscale Sn off-centering behind low thermal conductivity in SnSe thermoelectric. https://arxiv.org/abs/2301.05773

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