Impact of Metal Cation on Chiral Properties of 2D Halide Perovskites

TL;DR

This study examines how different metal cations influence the structural and phonon chirality in 2D halide perovskites, revealing that Sn increases phonon chirality without significantly affecting structural chirality.

Contribution

It provides new insights into the role of metal cations in modulating phonon and structural chirality in chiral 2D halide perovskites.

Findings

Sn incorporation distorts metal halide octahedra but minimally affects structural chirality.

MBA$_{2}$SnI$_{4}$ exhibits significantly more chiral phonons than MBA$_{2}$PbI$_{4}$.

Enhanced phonon chirality does not produce larger angular momentum under temperature gradients.

Abstract

Chiral two-dimensional (2D) halide perovskites are formed by embedding chiral organic cations in a perovskite crystal structure. The chirality arises from distortions of the 2D metal halide layers induced by the packing of these organic cations. Sn-based octahedra spontaneously distort, but it remains unclear whether this intrinsic structural instability enhances the chirality. We investigate the effect of the metal cation on structural and phonon chirality in MBA$_{2}$Sn$_{\mathrm{x}}$Pb$_{1-\mathrm{x}}$I$_{4}$ (x = 0, 1/2, and 1). Incorporating Sn does distort the metal halide octehedra, yet it only has a minor impact on the structural chirality. In contrast, the phonons in MBA$_{2}$SnI$_{4}$ are substantially more chiral than in MBA$_{2}$PbI$_{4}$, especially the in-plane acoustic modes. However, this enhanced phonon chirality does not lead to a generation of a larger angular momentum under a temperature gradient, because the contributions of different chiral phonons tend to compensate one another.