钙钛矿超晶格中二维平坦极性带导致的不可约亚纳米平方铁电畴
Irreducible sub-nm$^2$ ferroelectric domains by 2D-flat polar band in perovskite superlattices
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中文总结 AI 辅助
在钙钛矿超晶格中发现二维平坦极性带，产生不可约亚纳米平方铁电畴，密度超300 Tbit/cm²，为超高密度低功耗存储器件提供新途径。
中文摘要 AI 辅助
铁电体中的平坦极性声子带被设想用于实现不可约小畴，以达到最高存储密度。然而，此类能带极为罕见，仅在铁电氧化铪中发现了一维平坦极性带，其产生宽度为2.7埃（半晶胞宽度）的不可约窄线型畴。在此，我们报道在铁电(BaTiO$_3$)$_1$/(BaXO$_3$)$_1$超晶格（X = Zr, Sn）中发现二维平坦极性带，该能带在其四分之一晶胞面积内产生高度局域化、非相互作用的偶极子，形成不可约亚纳米平方铁电畴的准简并态。估算的铁电畴密度超过300 Tbit/cm$^2$（假设每畴一位），在已知铁电体中创下纪录，且偶极子可在低电压下独立切换。承载二维平坦带的铁电相在超晶格堆叠方向上构成竞争基态，因此可在自由 standing 结构和MgO衬底上的外延生长中实验实现。这一发现为探索铁电体中多维平坦极性带以及设计超高密度、低功耗存储器件开辟了前所未有的机遇。
英文摘要
Flat polar phonon bands in ferroelectrics have been envisioned to realize irreducibly small domains for achieving the highest memory density. However, such bands are extremely rare, with only a one-dimensional flat polar band discovered in ferroelectric hafnia, which gives rise to irreducibly narrow, line-type domains with a half-unit-cell width of 2.7 Angstrom. Here, we report the discovery of a two-dimensional flat polar band in the ferroelectric (BaTiO$_3$)$_1$/(BaXO$_3$)$_1$ superlattice (X = Zr, Sn), which generates extremely localized, noninteracting dipoles within its quarter-unit-cell area that form quasi-degenerate states of irreducible sub-nm$^2$ ferroelectric domains. The estimated ferroelectric domain density, exceeding 300 Tbit/cm$^2$ (assuming one bit per domain) represents a record high among the known ferroelectrics, with independently switchable dipoles at low voltages. The ferroelectric phase hosting two-dimensional flat bands constitutes a competing ground state across superlattice stacking directions and thus can be experimentally realized in both freestanding structures and epitaxial growth on MgO substrates. This discovery opens unprecedented opportunities to explore multidimensional flat polar bands in ferroelectrics and to engineer ultra-dense and low-power memory devices.
发表机构
- Ulsan National Institute of Science and Technology (UNIST)（蔚山科学技术院）
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