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Published on: March 19, 2017
Hidden Chiral Ferroelectricity in AgNbO_{3} Perovskite
Ying Song1,2, Lingzhi Cao1,2, Jinming Zhai1,2
1University of Science and Technology Beijing, Key Laboratory of Advanced Materials and Devices for Post-Moore Chips, Ministry of Education, Beijing 100083, China.
None:
AgNbO_{3} is a lead-free perovskite with considerable potential for energy storage and optoelectronic applications, yet its low-temperature crystal structure has remained controversial. In this Letter, we revisit its low-energy structural landscape using a systematic first-principles structural search based on symmetry-adapted phonon-mode theory. We uncover a previously unreported chiral ferroelectric phase with space group R3, which exhibits a large spontaneous polarization and a low polarization switching barrier, enabling polarization reversal under electric fields. Crucially, the structural chirality of this phase is intrinsically locked to the ferroelectric polarization, allowing electrical control of the chiral handedness. Consequently, chiral optical responses-including circular dichroism, circular photogalvanic effect, optical activity, and second-order nonlinear optics-can be reversibly switched by an external electric field. These results not only clarify the complex low-temperature structural behavior of AgNbO_{3} but also establish a rare purely inorganic platform for electric-field-tunable chirality, opening a pathway toward ultrafast, electrically controlled chiral optoelectronics.
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