Wang Lei, Shih En-Min, Ghiotto Augusto, Xian Lede, Rhodes Daniel A, Tan Cheng, Claassen Martin, Kennes Dante M, Bai Yusong, Kim Bumho, Watanabe Kenji, Taniguchi Takashi, Zhu Xiaoyang, Hone James, Rubio Angel, Pasupathy Abhay N, Dean Cory R
National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
Department of Physics, Columbia University, New York, NY, USA.
Nat Mater. 2020 Aug;19(8):861-866. doi: 10.1038/s41563-020-0708-6. Epub 2020 Jun 22.
In narrow electron bands in which the Coulomb interaction energy becomes comparable to the bandwidth, interactions can drive new quantum phases. Such flat bands in twisted graphene-based systems result in correlated insulator, superconducting and topological states. Here we report evidence of low-energy flat bands in twisted bilayer WSe, with signatures of collective phases observed over twist angles that range from 4 to 5.1°. At half-band filling, a correlated insulator appeared that is tunable with both twist angle and displacement field. At a 5.1° twist, zero-resistance pockets were observed on doping away from half filling at temperatures below 3 K, which indicates a possible transition to a superconducting state. The observation of tunable collective phases in a simple band, which hosts only two holes per unit cell at full filling, establishes twisted bilayer transition metal dichalcogenides as an ideal platform to study correlated physics in two dimensions on a triangular lattice.
在库仑相互作用能与带宽相当的窄电子带中，相互作用可驱动新的量子相。基于扭曲石墨烯的系统中的此类平带会导致关联绝缘体、超导态和拓扑态。在此，我们报告了扭曲双层WSe₂中低能平带的证据，在4°至5.1°的扭曲角范围内观察到了集体相的特征。在半带填充时，出现了一种与扭曲角和位移场都可调的关联绝缘体。在5.1°的扭曲下，在低于3 K的温度下，在远离半填充的掺杂时观察到零电阻口袋，这表明可能向超导态转变。在一个简单能带中观察到可调谐的集体相，该能带在完全填充时每个晶胞仅容纳两个空穴，这确立了扭曲双层过渡金属二硫属化物作为在三角晶格上研究二维关联物理的理想平台。
