Pressure-induced ferroelectric-like transition creates a polar metal in defect antiperovskites Hg<sub>3</sub>Te<sub>2</sub>X<sub>2</sub> (X = Cl, Br).
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33686062.
- Also identified by DOI 10.1038/s41467-021-21836-7 and PMC identifier 7940478.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Ferroelectricity is typically suppressed under hydrostatic compression because the short-range repulsions, which favor the nonpolar phase, increase more rapidly than the long-range interactions, which prefer the ferroelectric phase. Here, based on single-crystal X-ray diffraction and density-functional theory, we provide evidence of a ferroelectric-like transition from phase I2<sub>1</sub>3 to R3 induced by pressure in two isostructural defect antiperovskites Hg<sub>3</sub>Te<sub>2</sub>Cl<sub>2</sub> (15.5 GPa) and Hg<sub>3</sub>Te<sub>2</sub>Br<sub>2</sub> (17.5 GPa). First-principles calculations show that this transition is attributed to pressure-induced softening of the infrared phonon mode Γ<sub>4</sub>, similar to the archetypal ferroelectric material BaTiO<sub>3</sub> at ambient pressure. Additionally, we observe a gradual band-gap closing from ~2.5 eV to metallic-like state of Hg<sub>3</sub>Te<sub>2</sub>Br<sub>2</sub> with an unexpectedly stable R3 phase even after semiconductor-to-metal transition. This study demonstrates the possibility of emergence of polar metal under pressure in this class of materials and establishes the possibility of pressure-induced ferroelectric-like transition in perovskite-related systems.