Visualizing broken symmetry and topological defects in a quantum Hall ferromagnet
Visualizing broken symmetry and topological defects in a quantum Hall ferromagnet
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DOI：
10.1126/science.abm3770
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发表时间：
2022-01-21
期刊：
影响因子：
56.9
通讯作者：
Yazdani, Ali
中科院分区：
文献类型：
--
作者：
Liu, Xiaomeng;Farahi, Gelareh;Yazdani, Ali
在强磁场下，石墨烯中电子之间的相互作用驱动形成了一组丰富的量子霍尔铁磁（QHFM）相，这些相具有破缺的自旋或谷对称性。利用扫描隧道光谱（STS）可视化原子尺度的电子波函数，我们解析了石墨烯QHFM相的谷有序的微观特征和分数量子霍尔相的光谱特征。在电荷中性条件下，我们观察到一个从谷极化态到谷间相干态的场调谐连续量子相变，其电子密度存在凯库勒畸变。映射谷纹理提取的STS测量的凯库勒相，我们可以可视化谷skyrmion激发附近的带电缺陷。我们的技术可以应用于检查谷有序相和它们的拓扑激发在广泛的材料。
The interaction between electrons in graphene under high magnetic fields drives the formation of a rich set of quantum Hall ferromagnetic (QHFM) phases with broken spin or valley symmetry. Visualizing atomic-scale electronic wave functions with scanning tunneling spectroscopy (STS), we resolved microscopic signatures of valley ordering in QHFM phases and spectral features of fractional quantum Hall phases of graphene. At charge neutrality, we observed a field-tuned continuous quantum phase transition from a valley-polarized state to an intervalley coherent state, with a Kekule distortion of its electronic density. Mapping the valley texture extracted from STS measurements of the Kekule phase, we could visualize valley skyrmion excitations localized near charged defects. Our techniques can be applied to examine valley-ordered phases and their topological excitations in a wide range of materials.