Mott and generalized Wigner crystal states in WSe2/WS2 moire superlattices
Mott and generalized Wigner crystal states in WSe2/WS2 moire superlattices
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DOI：
10.1038/s41586-020-2092-4
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发表时间：
2020-03-01
期刊：
影响因子：
64.8
通讯作者：
Wang, Feng
中科院分区：
文献类型：
--
作者：
Regan, Emma C.;Wang, Danqing;Wang, Feng
在WSe 2/WS 2莫尔超晶格中检测到了强关联绝缘Mott相和广义Wigner相，并利用光学技术研究了它们的电学性质和激发自旋态.莫尔超晶格可用于在二维货车德瓦尔斯异质结构中设计强关联电子态，正如最近在魔角扭曲双层石墨烯和ABC三层石墨烯中观察到的相关绝缘和超导态所证明的那样，氮化硼莫尔超晶格（1-4）。过渡金属二硫属化物云纹异质结构提供了另一个模型系统的相关量子现象的研究（5），因为它们的强光-物质相互作用和大的自旋-轨道耦合。然而，在这个系统中的相关绝缘状态的实验观察是具有挑战性的传统的传输技术。在这里，我们报告的光学检测的强关联相的半导体WSe 2/WS 2莫尔超晶格。我们使用灵敏的光学检测技术，揭示了每个超晶格位置一个空穴处的Mott绝缘体状态和超晶格1/3和2/3填充处的令人惊讶的绝缘相，我们将其归因于基础晶格上的广义Wigner结晶（6-11）。此外，自旋谷光学选择规则（12-14）的过渡金属二硫属化物异质结构，使我们能够光学创建和研究低能量激发自旋态的莫特绝缘体。我们测量一个非常长的自旋弛豫寿命为许多微秒的莫特绝缘状态，数量级长于电荷激发。我们的研究突出了使用莫尔超晶格超越石墨烯来探索相关物理的价值。
Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe2/WS2 moire superlattices, and their electrical properties and excited spin states are studied using an optical technique.Moire superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire superlattices(1-4). Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena(5) because of their strong light-matter interactions and large spin-orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice(6-11). Furthermore, the spin-valley optical selection rules(12-14) of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire superlattices beyond graphene to explore correlated physics.