Research of the Free-Carrier-Induced Ferroelectric Metal in Layered Perovskite Oxides

铁电金属将铁电性和金属性这两种看似相互排斥的性质结合在一起，引起了研究界的强烈反响。铁电体具有自发和可逆的电极化，具有广泛的应用前景，并提出了许多基本问题。一般来说，它们是绝缘体。引入流动载流子有望屏蔽长程库仑力和淬灭铁电性。Anderson和Blount从理论上提出了类铁电金属的存在，并在实验中观察到LiOsO3中金属的类铁电结构转变，打破了这一传统观念。虽然已经报道了一些铁电/极性金属的理论预测，但到目前为止，实验观察仍然相当罕见。本项目的核心问题是扩展该材料家族的成员，研究铁电/极性金属材料的非常规性能。我们在2022财年实现了两件事。首先，成功合成了一种在低温下具有类铁电结构转变的新型过渡金属氧化物（与LiOsO3相同）。其次，制备了一系列具有Ruddlesden-Popper型结构的载流子掺杂层状钙钛矿氧化物。

Ferroelectric metals combining ferroelectricity and metallicity, two seemingly mutually exclusive properties in one system, strongly stirred the research community. Ferroelectrics with a spontaneous and reversible electric polarization, are promising for a wide range of applications and pose a number of fundamental questions. In general, they are insulators. Introducing itinerant charge carriers is expected to screen the long-range coulomb forces and quench ferroelectricity. This conventional concept was broken when the existence of ferroelectric-like metal was theoretically proposed by Anderson and Blount and the ferroelectric-like structural transition in metallic was experimentally observed in LiOsO3. Although several theoretical predictions of ferroelectric/polar metals have been reported, the experimental observations are still rather rare so far. The core issue of this project is to extend the members of this material family and research the unconventional properties of ferroelectric/polar metal materials.We have achieved two things in the fiscal year 2022 (FY2022). First, one new metallic transition metal oxide (same to LiOsO3) with ferroelectric-like structural transition at low temperature was successfully synthesized in polycrystalline form. Second, a series of carrier doped layered perovskite oxides with Ruddlesden-Popper type structure was prepared.