2020/09/30 by K. Geirhos, J. Langmann, Jan Langmann +14
Chemistry · Materials Science · Physics and Astronomy · #Antiferroelectricity #Chemistry #Cluster (spacecraft) #Condensed matter physics #Crystallography #Dielectric #Dielectric properties of ceramics #Ferroelectric and Piezoelectric Materials #Ferroelectricity #Ion #Jahn–Teller effect #Materials science #Multiferroics and related materials #Order (exchange) #Phase (matter) #Phase transition #Physics #Quantum mechanics #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.126.187601
published as Phys. Rev. Lett. 126, 187601 (2021)
arxiv created 2021/04/13 · openalex publication_date 2021/05/04 · arxiv updated 2021/05/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We report the observation of an antipolar phase in cubic GaNb4S8 driven by an unconventional microscopic mechanism, the cooperative Jahn-Teller effect of Nb4S4 molecular clusters. The assignment of the antipolar nature is based on sudden changes in the crystal structure and a strong drop of the dielectric constant at TJT=31 K, also indicating the first-order nature of the transition. In addition, we found that local symmetry lowering precedes long-range orbital ordering, implying the presence of a dynamic Jahn-Teller effect in the cubic phase above TJT. Based on the variety of structural polymorphs reported in lacunar spinels, also including ferroelectric phases, we argue that GaNb4S8 may be transformable to a ferroelectric state, which would further classify the observed antipolar phase as antiferroelectric.