Predicting the Structural, Electronic and Magnetic Properties of Few Atomic-layer Polar Perovskite

Abstract

Density functional theory (DFT) calculations are performed to predict the structural, electronic and magnetic properties of electrically neutral or charged few-atomic-layer (AL) oxides whose parent systems are based on polar perovskite $KTa{O}_3$. Their properties vary greatly with the number of ALs ($n_{AL}$) and the stoichiometric ratio. In the few-AL limit ($n_{AL}⩽14$), the even AL (EL) systems with chemical formula $(KTa{O}_3{)}_n$ are semiconductors, while the odd AL (OL) systems with formula ($K_{n+1}T{a}_n{O}_{3n+1}$ or $K_{n}T{a}_{n+1}{O}_{3n+2}$) are half-metal except for the unique $KT{a}_2{O}_5$ case which is a semiconductor due to the large Peierls distortions. After reaching certain critical thickness ($n_{AL}>14$), the EL systems show ferromagnetic surface states, while ferromagnetism disappears in the OL systems. These predictions from fundamental complexity of polar perovskite when approaching the two-dimensional (2D) limit may be helpful for interpreting experimental observations later.

Phys. Chem. Chem. Phys., 2021