Ferroelectric Chirality-Driven Direction-Tunable and Spin-Invertible Corner States in 2D MOF-Based Magnetic Second-Order Topological Insulators

TL;DR

This paper introduces a novel method to control spin-polarized corner states in 2D magnetic second-order topological insulators by inducing ferroelectric chirality in flexible metal-organic frameworks, enabling real-space and spin-space manipulation.

Contribution

It demonstrates the first approach to simultaneously manipulate corner states in real space and spin space using ferroelectric chirality in 2D MOF-based magnetic SOTIs.

Findings

Cr(2-pyzol)2 is a new 2D magnetic SOTI with ferroelectric chirality.

Corner states can be directionally tuned in real space.

Corner states can be spin-inverted upon ferroelectric chirality switching.

Abstract

Despite the rapid progress in predicting 2D magnetic second-order topological insulators (SOTIs), effective strategies for manipulating their spin-polarized corner states remain largely unexplored. The interplay between ferroelectricity, chirality, magnetism, and topology presents an untapped opportunity for controlling these corner states. Here, we propose a novel approach for tuning spin-polarized corner states in 2D magnetic SOTIs by inducing ferroelectric chirality in 2D metal-organic frameworks (MOFs) with intrinsic structural flexibility. Through symmetry analysis, we strategically replace pyrazine (pyz) ligands with 2-pyrazinolate (2-pyzol) ligands in the 2D MOF Cr(pyz)2, leading to the emergence of a new 2D magnetic SOTI, Cr(2-pyzol)2, which facilitates ferroelectric chirality controlled spin-polarized corner states in both spin channels. Through first-principle calculations, we demonstrate that Cr(2-pyzol)2 belongs to ferroelectric chiral systems, and its corner states can be directionally tuned in real space and spin-inverted in spin space upon ferroelectric chirality switching. Our work represents the first attempt to simultaneously manipulate corner states in both real space and spin space, offering a new strategy for integrating ferroelectric chirality into 2D MOF-based magnetic SOTIs.