2020/09/30 by Yubo Qi, Andrew M. Rappe
Engineering · Materials Science · Physics and Astronomy · #Acoustic Wave Resonator Technologies #Advanced Sensor and Energy Harvesting Materials #Composite material #Condensed matter physics #Dielectric #Dipole #Ferroelectric and Piezoelectric Materials #Ferroelectricity #Materials science #Molecule #Physics #Piezoelectricity #Quantum mechanics #cond-mat.mtrl-sci #van der Waals force
paper · pdf · doi:10.1103/physrevlett.126.217601
published as Phys. Rev. Lett. 126, 217601 (2021)
arxiv created 2021/04/20 · openalex publication_date 2021/05/26 · arxiv updated 2021/06/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
In this study, we investigate the underlying mechanisms of the universal negative piezoelectricity in low-dimensional layered materials by carrying out first-principles calculations. Two-dimensional layered ferroelectric CuInP2S6 is analyzed in detail as a typical example, but the theory can be applied to any other low-dimensional layered piezoelectrics. Consistent with the theory proposed in [Phys. Rev. Lett. 119, 207601 (2017)PRLTAO0031-900710.1103/PhysRevLett.119.207601, the anomalous negative piezoelectricity in CuInP2S6 also results from its negative clamped-ion term, which cannot be compensated by the positive internal-strain part. Here, we focus on a more general rule by proposing that having a negative clamped-ion term should be universal among piezoelectric materials, which is attributed to the "lag of Wannier center" effect. The internal-strain term, which is the change in polarization due to structural relaxation in response to strain, is mostly determined by the spatial structure and chemical bonding of the material. In a low-dimensional layered piezoelectric material such as CuInP2S6, the internal-strain term is approximately zero. This is because the internal structure of the molecular layers, which are bonded by the weak van der Waals interaction, responds little to the strain. As a result, the magnitude of the dipole, which depends strongly on the dimension and structure of the molecular layer, also has a small response with respect to strain. An equation bridging the internal strain responses in low-dimensional and three-dimensional piezoelectrics is also derived to analytically express this point. This work aims to deepen our understanding about this anomalous piezoelectric effect, especially in low-dimensional layered materials, and provide strategies for discovering materials with novel electromechanical properties.