近日，美国加州大学圣巴巴拉分校物理系的Andrea F. Young及其研究团队取得一项新进展。经过不懈努力，他们实现了扭曲二碲化钼中分数量子陈绝缘体的直接磁成像。相关研究成果已于2024年11月20日在国际权威学术期刊《自然》上发表。

本研究利用纳米级超导传感器，绘制了扭曲双层二碲化钼（MoTe?）中的磁边缘场分布图，先前的输运和光学传感实验已在该材料中揭示了零磁场下分数量子陈绝缘体（FCI）态的形成。研究人员观察到与首个莫尔空穴带填充ν=1、2/3、3/5、4/7和5/9相关的局部磁场振荡，这与在这些填充下形成FCI相一致。

研究人员确定了最稳健的FCI态（ν=-2/3）的局部热力学能隙，发现-2/3Δ高达7毫电子伏特。研究人员还对样品的空间无序性进行了表征，发现其主要由有效晶胞面积的不均匀性，以及带边偏移和束缚偶极矩的不均匀性所主导。这项研究结果既揭示了结构无序性，在研究扭曲同质双层莫尔系统时所带来的挑战，也展现了底层相关拓扑态的稳健性所带来的机遇。

据悉，轨道磁化是探测拓扑结构和相互作用的一种灵敏手段，在陈绝缘体中表现尤为丰富，因为其中的拓扑边缘态承载着大平衡电流。

附：英文原文

Title: Direct magnetic imaging of fractional Chern insulators in twisted MoTe₂

Author: Redekop, Evgeny, Zhang, Canxun, Park, Heonjoon, Cai, Jiaqi, Anderson, Eric, Sheekey, Owen, Arp, Trevor, Babikyan, Grigory, Salters, Samuel, Watanabe, Kenji, Taniguchi, Takashi, Huber, Martin E., Xu, Xiaodong, Young, Andrea F.

Issue&Volume: 2024-11-20

Abstract: Orbital magnetization provides a sensitive probe of topology and interactions, with particularly rich phenomenology in Chern insulators in which the topological edge states carry large equilibrium currents. Here we use a nanoscale superconducting sensor to map the magnetic fringe fields in twisted bilayers of MoTe₂, in which transport and optical sensing experiments have revealed the formation of fractional Chern insulator (FCI) states at zero magnetic field. We observe oscillations in the local magnetic field associated with fillings ν=1, 2/3, 3/5, 4/7 and 5/9 of the first moiré hole band, consistent with the formation of FCIs at these fillings. We determine the local thermodynamic gaps of the most robust FCI state at ν=-2/3, finding ^-2/3Δ as large as 7meV. We also characterize sample spatial disorder, which is dominated by both inhomogeneity in the effective unit cell area as well as inhomogeneity in the band edge offset and bound dipole moment. Our results highlight both the challenges posed by structural disorder in the study of twisted homobilayer moiré systems and the opportunities afforded by the robust nature of the underlying correlated topological states.

DOI: 10.1038/s41586-024-08153-x

Source: https://www.nature.com/articles/s41586-024-08153-x