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<p>Two-dimensional transition metal dichalcogenides (TMDs) heterostructures formed moiré superlattices have emerged as a new platform for exploring correlated excitonic states and valleytronic phenomena. Despite the significant progress in moiré-trapped single excitons, the valley polarization and fine structure of moiré-trapped biexcitons remain poorly understood, with the existing studies reporting only limited or zero polarization and lacking insight into the underlying mechanisms. Here, we study the moiré-trapped interlayer biexcitons in WS<sub>2</sub>/WSe<sub>2</sub> heterostructures through power- and temperature-dependent photoluminescence (PL) spectroscopy. We find that the valley polarization of these biexcitons can be effectively tuned, reaching ~<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(55\%\)</EquationSource> <EquationSource Format="MATHML"><math> <mn>55</mn> <mi>%</mi> </math></EquationSource> </InlineEquation> at 120 K. This behavior is attributed to the different occupation of intravalley and intervalley biexcitons within the fine structure, with the intravalley biexcitons playing a dominant role. The power-dependent energy splitting and temperature-dependent polarization trends further confirm the existence of biexciton fine structure and its influence on valley polarization. Furthermore, the experiment revealed a fine structure splitting of 2.77 meV, consistent with theoretical calculations. Our study provides new insight into the rational control of excitonic states in moiré superlattices and establishes a basis for developing advanced valleytronic devices, such as polarization-sensitive photodetectors and quantum light sources.</p>

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Tuning valley polarization of moiré trapped biexcitons by fine structure occupation in WS2/WSe2 heterostructures

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月26日

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  • Yufei Jiang,
  • Yongzhi She,
  • Xinke Cheng,
  • Qinghai Tan,
  • Jinlong Yang,
  • Yilong Zhao,
  • Peiwu Liu,
  • Min Wu,
  • Xiaotian Dai,
  • Zengkai Wang,
  • Hongbing Cai,
  • Nan Pan,
  • Xiaoping Wang

摘要

Two-dimensional transition metal dichalcogenides (TMDs) heterostructures formed moiré superlattices have emerged as a new platform for exploring correlated excitonic states and valleytronic phenomena. Despite the significant progress in moiré-trapped single excitons, the valley polarization and fine structure of moiré-trapped biexcitons remain poorly understood, with the existing studies reporting only limited or zero polarization and lacking insight into the underlying mechanisms. Here, we study the moiré-trapped interlayer biexcitons in WS2/WSe2 heterostructures through power- and temperature-dependent photoluminescence (PL) spectroscopy. We find that the valley polarization of these biexcitons can be effectively tuned, reaching ~ \(55\%\) 55 % at 120 K. This behavior is attributed to the different occupation of intravalley and intervalley biexcitons within the fine structure, with the intravalley biexcitons playing a dominant role. The power-dependent energy splitting and temperature-dependent polarization trends further confirm the existence of biexciton fine structure and its influence on valley polarization. Furthermore, the experiment revealed a fine structure splitting of 2.77 meV, consistent with theoretical calculations. Our study provides new insight into the rational control of excitonic states in moiré superlattices and establishes a basis for developing advanced valleytronic devices, such as polarization-sensitive photodetectors and quantum light sources.