Observation of room-temperature polar skyrmions
Observation of room-temperature polar skyrmions
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DOI：
10.1038/s41586-019-1092-8
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发表时间：
2019-04-18
期刊：
影响因子：
64.8
通讯作者：
Ramesh, R.
中科院分区：
文献类型：
--
作者：
Das, S.;Tang, Y. L.;Ramesh, R.
复杂的拓扑结构是探索凝聚态物理中涌现现象和奇异相的肥沃土壤。例如，最近在（PbTiO 3）（n）/（SrTiO 3）（n）超晶格中发现极化涡旋及其相关的复相共存和在施加电场下的响应，表明存在能够产生有趣的物理响应（例如手性、负电容和大的压电响应）的复杂多维系统（1-3）。在这里，通过不同的外延限制，我们发现室温下的极化skyrmion气泡在钛酸铅层限制钛酸锶层，这是由原子分辨率扫描透射电子显微镜成像。相场模型和第二原理计算显示，极性skyrmion气泡的skyrmion数为+1，共振软X射线衍射实验显示圆二色性，证实了手性。这种纳米尺度的极性skyrmion气泡是磁性skyrmion的电类似物，并可能有助于铁电体向结合涌现手性和电可控负电容的功能性的进步。
Complex topological configurations are fertile ground for exploring emergent phenomena and exotic phases in condensed-matter physics. For example, the recent discovery of polarization vortices and their associated complex-phase coexistence and response under applied electric fields in superlattices of (PbTiO3)(n)/(SrTiO3)(n) suggests the presence of a complex, multi-dimensional system capable of interesting physical responses, such as chirality, negative capacitance and large piezo-electric responses(1-3). Here, by varying epitaxial constraints, we discover room-temperature polar-skyrmion bubbles in a lead titanate layer confined by strontium titanate layers, which are imaged by atomic-resolution scanning transmission electron microscopy. Phase-field modelling and second-principles calculations reveal that the polar-skyrmion bubbles have a skyrmion number of +1, and resonant soft-X-ray diffraction experiments show circular dichroism, confirming chirality. Such nanometre-scale polar-skyrmion bubbles are the electric analogues of magnetic skyrmions, and could contribute to the advancement of ferroelectrics towards functionalities incorporating emergent chirality and electrically controllable negative capacitance.