International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Phys Rev Lett. 2018 Aug 31;121(9):096401. doi: 10.1103/PhysRevLett.121.096401.
A flatband representing a highly degenerate and dispersionless manifold state of electrons may offer unique opportunities for the emergence of exotic quantum phases. To date, definitive experimental demonstrations of flatbands remain to be accomplished in realistic materials. Here, we present the first experimental observation of a striking flatband near the Fermi level in the layered Fe_{3}Sn_{2} crystal consisting of two Fe kagome lattices separated by a Sn spacing layer. The band flatness is attributed to the local destructive interferences of Bloch wave functions within the kagome lattices, as confirmed through theoretical calculations and modelings. We also establish high-temperature ferromagnetic ordering in the system and interpret the observed collective phenomenon as a consequence of the synergetic effect of electron correlation and the peculiar lattice geometry. Specifically, local spin moments formed by intramolecular exchange interaction are ferromagnetically coupled through a unique network of the hexagonal units in the kagome lattice. Our findings have important implications to exploit emergent flat-band physics in special lattice geometries.
一个代表高度简并和无弥散的电子简并态的能带可能为奇异量子相的出现提供独特的机会。迄今为止，在实际材料中实现能带的明确实验演示仍然有待完成。在这里，我们首次在由两个 Fe kagome 晶格通过 Sn 间隔层隔开的层状 Fe_3Sn_2 晶体中观察到了在费米能级附近的显著的平带。能带的平坦度归因于 kagome 晶格内 Bloch 波函数的局部破坏性干涉，这通过理论计算和模型得到了证实。我们还在系统中建立了高温铁磁有序，并将观察到的集体现象解释为电子相关和特殊晶格几何的协同效应的结果。具体而言，由分子间交换相互作用形成的局域自旋矩通过 kagome 晶格中六边形单元的独特网络铁磁耦合。我们的发现对于利用特殊晶格几何中的新兴平带物理具有重要意义。
