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 based on polar perovskite KTaO₃. 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 the chemical formula (KTaO₃)_n are semiconductors, while the odd AL (OL) systems with the formula K_n+1Ta_nO_3n+1 or K_nTa_n+1O_3n+2 are half-metal except for the unique KTa₂O₅ case which is a semiconductor due to the large Peierls distortions. After reaching a 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.