2022 Fiscal Year Final Research Report

Proving experimentally "Colossal proximity of ferroelectric polarization"

Research Project

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Project/Area Number	19K21853
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 13:Condensed matter physics and related fields
Research Institution	University of Hyogo (2022) Kyushu University (2019-2021)
Principal Investigator	Yukio Watanabe 兵庫県立大学, 工学研究科, 非常勤研究員 (40274550)
Co-Investigator(Kenkyū-buntansha)	藤澤浩訓兵庫県立大学, 工学研究科, 教授 (30285340) 佐藤琢哉東京工業大学, 理学院, 教授 (40451885) 横田紘子千葉大学, 大学院理学研究院, 准教授 (50608742)
Project Period (FY)	2019-06-28 – 2023-03-31
Keywords	ferroelectric / surface / polarization / 2D / proximity
Outline of Final Research Achievements	Textbooks teach that the application of electric field above a threshold between a pair of electrodes orient spontaneous polarization. In this study, such orientation was world-first discovered in electrodeless regions. For this, adsorbates need to be removed from surfaces, conventionally through high-T annealing in UHV. Because such annealing creates defects, we use atomic oxygen at RT in UHV and obtain atomically flat surface where defects are substantially removed. Under some conditions, spontaneous polarization aligned reproducibly in a macroscopic region of free surface far from electrodes where field from electrodes are negligible. Through measurements of macrospcopic and nanoscopic polarization and conduction, we show that this phenomenon, which we call macroscopic proximity effect, exists and propose a mechanism through ab initio calculations and finite element method analyses.
Free Research Field	ferroelectric
Academic Significance and Societal Importance of the Research Achievements	本研究は，既存理論では予想さえされていなかっ新現象をた世界で初めて報告するものである．この代表者らの提案する機構からすると，実用上重要な金属酸化物系の強誘電体一般に起こる、原理的な現象と予想されるので，幅広い意義を持つと考えられる．例えば，、強誘電体の基礎である自発分極のダイナミクスの新概念に繋がる可能性があり電極やエッチングを用いない革新的な分極の制御技術を創生する高い可能性があると考えられる．このため、応用・基礎を革新する新現象として、分野を超えての意義があると考えられる．