[125] Local electronic band structure around ferroelectric domain wall in metastable HfO₂

Both experimental and theoretical studies have reported that ideal HfO₂ is stable in its paraelectric phase at room temperature. However, ferroelectric phases are metastable and can be stabilized through external controls such as chemical substitution, strain, or surface energy. Unlike typical ferroelectric perovskites, HfO₂ exhibits unique domain wall (DW) behavior. The energy increase at the boundary between oppositely polarized domains is comparatively small or even negative, suggesting that high-density ferroelectric DWs may be energetically favorable. Its low symmetry allows for various types of ferroelectric DWs. In this study, we investigate these diverse domain structures and examine the local electronic band structure around the ferroelectric DWs of metastable orthorhombic HfO₂ (space group Pca2₁). Our findings reveal a band gap reduction of up to approximately 4%, confirming that this electronic shift is directly induced by the presence of ferroelectric DWs.