Local Sn Dipolar-Character Displacements behind the 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

doi:10.1103/PhysRevLett.131.036101

Local Sn Dipolar-Character Displacements behind the Low Thermal Conductivity in SnSe Thermoelectric

Phys Rev Lett. 2023 Jul 21;131(3):036101. doi: 10.1103/PhysRevLett.131.036101.

Authors

E S Bozin¹, H Xie², A M M Abeykoon³, S M Everett⁴, M G Tucker⁴, M G Kanatzidis², S J L Billinge⁵

Affiliations

¹ Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA.
² Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
³ Photon Sciences Division, Brookhaven National Laboratory, Upton, New York 11973, USA.
⁴ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
⁵ Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA.

PMID: 37540855
DOI: 10.1103/PhysRevLett.131.036101

Abstract

The local atomic structure of SnSe was characterized across its orthorhombic-to-orthorhombic structural phase transition using x-ray pair distribution function analysis. Substantial Sn displacements with a dipolar character persist in the high-symmetry high-temperature phase, albeit with a symmetry different from that of the ordered displacements below the transition. The analysis implies that the transition is neither order-disorder nor displacive but rather a complex crossover. Robust ferrocoupled SnSe intralayer distortions suggest a ferroelectriclike instability as the driving force. These local symmetry-lowering Sn displacements are likely integral to the ultralow lattice thermal conductivity mechanism in SnSe.