Wang Jue, Shi Qianhui, Shih En-Min, Zhou Lin, Wu Wenjing, Bai Yusong, Rhodes Daniel, Barmak Katayun, Hone James, Dean Cory R, Zhu X-Y
Department of Chemistry, Columbia University, New York, New York 10027, USA.
Department of Physics, Columbia University, New York, New York 10027, USA.
Phys Rev Lett. 2021 Mar 12;126(10):106804. doi: 10.1103/PhysRevLett.126.106804.
Charge separated interlayer excitons in transition metal dichalcogenide heterobilayers are being explored for moiré exciton lattices and exciton condensates. The presence of permanent dipole moments and the poorly screened Coulomb interaction make many-body interactions particularly strong for interlayer excitons. Here we reveal two distinct phase transitions for interlayer excitons in the MoSe_{2}/WSe_{2} heterobilayer using time and spatially resolved photoluminescence imaging: from trapped excitons in the moiré potential to the modestly mobile exciton gas as exciton density increases to n_{ex}∼10^{11} cm^{-2} and from the exciton gas to the highly mobile charge separated electron-hole plasma for n_{ex}>10^{12} cm^{-2}. The latter is the Mott transition and is confirmed in photoconductivity measurements. These findings set fundamental limits for achieving quantum states of interlayer excitons.
过渡金属二硫族化合物异质双层中的电荷分离层间激子正被用于探索莫尔激子晶格和激子凝聚态。永久偶极矩的存在以及屏蔽效果不佳的库仑相互作用使得层间激子的多体相互作用尤为强烈。在这里，我们使用时间和空间分辨光致发光成像揭示了MoSe₂/WSe₂异质双层中层间激子的两种不同相变：随着激子密度增加到n_ex ∼ 10¹¹ cm⁻²，从莫尔势中的捕获激子转变为适度移动的激子气体；对于n_ex > 10¹² cm⁻²，从激子气体转变为高度移动的电荷分离电子 - 空穴等离子体。后者是莫特转变，并在光电导率测量中得到证实。这些发现为实现层间激子的量子态设定了基本限制。
