Unveiling the\nRacemization in Ferroelectrics with\nCoupled Ferroelectricity and Optical Activity

The most distinctive features of\nferroelectrics are spontaneous\npolarization and depolarization. Ferroelectricity was first observed\nin Rochelle salt, a compound with a chiral component in which the\nmolecular chirality is not affected by depolarization. For structurally\nchiral ferroelectrics (SCFs), such as triglycine sulfate, which lacks\nchiral components, the depolarization effect on chirality presents\nan intriguing and unexplored topic. In this study, we focus on a newly\nproposed chiral optical topic in optically active ferroelectrics with\ncoupled ferroelectricity and optical activity. We examined the depolarization\neffect on the optical activity in these ferroelectric materials and\nemployed chiral-environment crystallization and solid-state circular\ndichroism (CD) techniques to elucidate the racemization-depolarization\nmechanism in an SCF for the first time. For polar and nonchiral optically\nactive ferroelectrics, optical activity is averaged out in the powder\nstate, resulting in no CD signal. Additionally, we experimentally\nvalidated the consistency between CD measurements and optical activity\ntheory across the four optically active point groups (<i>m</i>, <i>mm</i>2, 4̅, 4̅2<i>m</i>). These\nfindings could advance the development of chiral spintronic devices\nby leveraging coupled ferroelectricity and optical activity to tune\nthe spin selectivity.