Moiré polar vortex, flat bands and Lieb lattice in twisted bilayer BaTiO${}_3$

Abstract

Advances in material fabrication techniques and growth methods have opened up a new chapter for twistronics, in the form of twisted freestanding three-dimensional material membranes. Through first-principles calculations based on density functional theory, we investigate the crystal and electronic structures of twisted bilayer BaTiO${}_3$. Our findings reveal that large stacking fault energy leads to chiral in-plane vortex pattern that was recently observed in experiments. Moreover, we also found non-zero out-of-plane local dipole moments, indicating that the strong interlayer interaction might offer promising strategy to stabilize ferroelectric order in the two-dimensional limit. Remarkably, the vortex pattern in the twisted BaTiO${}_3$ bilayer support localized electronic states with quasi-flat bands, associated with the interlayer hybridization of oxygen $p_z$ orbitals. We found that the associated band width reaches a minimum at $\sim$19${}^{\circ }$ twisting, configuring the largest magic angle in moiré systems reported so far. Further, the moiré vortex pattern bears a striking resemblance to two interpenetrating Lieb lattices and corresponding tight-binding model provides a comprehensive description of the evolution the moiré bands with twist angle and reveals the topological nature of these states.

8 pages, 5 figures

References in corpus (5)

• Very large spontaneous electric polarization in BiFeO3 single crystals at room temperature and its evolution under cycling fields
• A 2D ferroelectric vortex lattice in twisted BaTiO3 freestanding layers
• Polar meron-antimeron networks in strained and twisted bilayers
• Designing Ultra-Flat Bands in Twisted Bilayer Materials at Large Twist Angles without specific degree
• Thru-Hole Epitaxy: Is Remote Epitaxy Really Remote?

Cited by in corpus (6)

• Prediction of polarization vortices, charge modulation, flat bands, and moiré magnetism in twisted oxide bilayers
• Moiré Collapse and Luttinger Liquids In Twisted Anisotropic Homobilayers
• Stacking-dependent electronic structure of ultrathin perovskite bilayers
• On the origin of the unusual strain morphologies and polar Moiré patterns in twisted ferroelectrics
• Switchable Topological Polar Textures in Freestanding Ultrathin Ferroelectric Oxides
• Sliding and superlubric moiré twisting ferroelectric transition in HfO2