Unique family of halide perovskites displays surprising behaviors under hydrostatic pressures

Topological insulators are a novel quantum state of matter with important properties for various applications. Yalameha et al. investigate the topological phase of a class of halide perovskites, CsSnX₃ (X=I, Br, Cl), under hydrostatic pressures.

CsSnX₃ materials are unique due to their breadth of remarkable properties, including their tunable bandgap, high optical absorption, broad adsorption spectrum, small carrier effective mass and high charge carrier mobility. The narrow band gap of these compounds makes them especially interesting for electronic, optoelectronic and photovoltaic applications.

The authors used density functional theory calculations to study structural, electronic and elastic properties of this perovskite class in the cubic phase. The key characteristics they monitored include the material’s Poisson’s ratio – its orthogonal response to strain – as well as its Pugh’s ratio, which relates to its brittleness or ductility.

They observed a sudden change in a number of properties of CsSnX_3, including its Poisson’s ratio and its Pugh’s ratio, when the applied pressure approaches the material’s topological phase transition. They also found that the applied pressure changes the energy gap of CsSnX₃, leading to a band inversion – an important factor in recognizing the material’s topological phase. They noted the observation of two different types of band inversion, an interesting result that warrants further investigation.

These characteristics open up opportunities for room-temperature light-emitting materials for use in photovoltaics, radiation detectors, LEDs and quantum computing applications. “It is hoped that these new materials will play an important role in the future of quantum computers,” said author Shahram Yalameha.

Source: “Insight into the topological phase and elastic properties of halide perovskites CsSnX₃ (X = I, Br, Cl) under hydrostatic pressures,” by Shahram Yalameha, Parviz Saeidi, Zahra Nourbakhsh, Aminollah Vaez, and Ali Ramazani, Journal of Applied Physics (2020). The article can be accessed at https://doi.org/10.1063/1.5125920 .