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| Main Authors: | , |
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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2512.00628 |
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| _version_ | 1866914174793154560 |
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| author | Jung, Seongjoo Birol, Turan |
| author_facet | Jung, Seongjoo Birol, Turan |
| contents | Born effective charge (BEC), a fundamental quantity in lattice dynamics and ferroelectric theory, provides a quantitative measure of linear polarization response to ionic displacements. However, it does not account for higher-order effects, which can play a significant role in certain materials, such as fluorite HfO$_2$. In this letter, we extend the BEC framework by introducing the concept of second-order dynamical charge and mode effective charge. Using first-principles calculations, we demonstrate that specific combinations of nonpolar phonon modes in many oxides can induce substantial second-order polarizations, reaching magnitudes comparable to those of intrinsically polar modes. Through a symmetry-based analysis of the charge density, we elucidate the microscopic origin of these effects, tracing them to variations in bond covalency and local electronic rearrangements. We also demonstrate large second-order mode effective charge in well-studied perovskites such as SrTiO$_3$, highlighting the generality of these phenomena. Our results reveal a previously unrecognized mechanism that drives polarization in crystalline solids, offering new insights into the design principles of next-generation ferroelectric, piezoelectric and multifunctional materials. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_00628 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Electric Polarization from Nonpolar Phonons Jung, Seongjoo Birol, Turan Materials Science Computational Physics Born effective charge (BEC), a fundamental quantity in lattice dynamics and ferroelectric theory, provides a quantitative measure of linear polarization response to ionic displacements. However, it does not account for higher-order effects, which can play a significant role in certain materials, such as fluorite HfO$_2$. In this letter, we extend the BEC framework by introducing the concept of second-order dynamical charge and mode effective charge. Using first-principles calculations, we demonstrate that specific combinations of nonpolar phonon modes in many oxides can induce substantial second-order polarizations, reaching magnitudes comparable to those of intrinsically polar modes. Through a symmetry-based analysis of the charge density, we elucidate the microscopic origin of these effects, tracing them to variations in bond covalency and local electronic rearrangements. We also demonstrate large second-order mode effective charge in well-studied perovskites such as SrTiO$_3$, highlighting the generality of these phenomena. Our results reveal a previously unrecognized mechanism that drives polarization in crystalline solids, offering new insights into the design principles of next-generation ferroelectric, piezoelectric and multifunctional materials. |
| title | Electric Polarization from Nonpolar Phonons |
| topic | Materials Science Computational Physics |
| url | https://arxiv.org/abs/2512.00628 |