中国物理B ›› 2025, Vol. 34 ›› Issue (7): 77103-077103.doi: 10.1088/1674-1056/adc191

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Anomalous ultrafast thermalization of photoexcited carriers in two-dimensional materials induced by orbital coupling

Zhuoqun Wen(文卓群)1,2,3, Haiyu Zhu(诸海渝)2,4, Wen-Hao Liu(刘文浩)5, Zhi Wang(王峙)5,†, Wen Xiong(熊稳)1,2,‡, and Xingzhan Wei(魏兴战)1,2,3,§   

  1. 1 Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China;
    2 Chongqing School, University of Chinese Academy of Sciences, Chongqing 400714, China;
    3 University of Chinese Academy of Sciences, Beijing 100049, China;
    4 School of Optoelectronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;
    5 State Key Laboratory of Semiconductor Physics and Chip Technologies, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
  • 收稿日期:2025-01-17 修回日期:2025-03-06 接受日期:2025-03-18 出版日期:2025-06-18 发布日期:2025-07-10
  • 通讯作者: Zhi Wang, Wen Xiong, Xingzhan Wei E-mail:wangzhi@semi.ac.cn;xiongwen@cigit.ac.cn;weixingzhan@cigit.ac.cn
  • 基金资助:
    Project supported by the Natural Science Foundation of Chongqing of China (Grant No. CSTB2023NSCQ-LZX0087) and the National Natural Science Foundation of China (Grant Nos. 62074021 and 12174380).

Anomalous ultrafast thermalization of photoexcited carriers in two-dimensional materials induced by orbital coupling

Zhuoqun Wen(文卓群)1,2,3, Haiyu Zhu(诸海渝)2,4, Wen-Hao Liu(刘文浩)5, Zhi Wang(王峙)5,†, Wen Xiong(熊稳)1,2,‡, and Xingzhan Wei(魏兴战)1,2,3,§   

  1. 1 Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China;
    2 Chongqing School, University of Chinese Academy of Sciences, Chongqing 400714, China;
    3 University of Chinese Academy of Sciences, Beijing 100049, China;
    4 School of Optoelectronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;
    5 State Key Laboratory of Semiconductor Physics and Chip Technologies, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
  • Received:2025-01-17 Revised:2025-03-06 Accepted:2025-03-18 Online:2025-06-18 Published:2025-07-10
  • Contact: Zhi Wang, Wen Xiong, Xingzhan Wei E-mail:wangzhi@semi.ac.cn;xiongwen@cigit.ac.cn;weixingzhan@cigit.ac.cn
  • Supported by:
    Project supported by the Natural Science Foundation of Chongqing of China (Grant No. CSTB2023NSCQ-LZX0087) and the National Natural Science Foundation of China (Grant Nos. 62074021 and 12174380).

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摘要： Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design. Photon absorption generates electron-hole pairs, and subsequent scatterings can induce ultrafast thermalization within a picosecond, forming a quasi-equilibrium distribution with overheated electrons. The high-energy tail of this distribution enables carriers to overcome energy barriers, thereby enhancing quantum efficiency - a phenomenon known as photothermionic emission (PTE). Despite its importance, the onset and mechanisms of PTE remain under debate. Using real-time time-dependent density functional theory (rt-TDDFT), we investigate ultrafast carrier thermalization in two-dimensional (2D) materials graphene and PtTe$_{2}$, and the results reveal distinct differences. In graphene, both electrons and holes thermalize into Fermi-Dirac distributions with good agreement to experiment, while PtTe$_{2}$ exhibits anomalous high-energy tails for both electrons and holes, deviating significantly from Fermi-Dirac behavior. We attribute this anomaly to differences in orbital coupling between the two materials, from which we derive design principles for identifying optimal PTE candidates and, ultimately, improving photodetector performance.

关键词: ultrafast phenomena, time-dependent density functional theory, photoelectronics, photo-thermionic emission, 2D materials, graphene, platinum ditelluride

Abstract: Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design. Photon absorption generates electron-hole pairs, and subsequent scatterings can induce ultrafast thermalization within a picosecond, forming a quasi-equilibrium distribution with overheated electrons. The high-energy tail of this distribution enables carriers to overcome energy barriers, thereby enhancing quantum efficiency - a phenomenon known as photothermionic emission (PTE). Despite its importance, the onset and mechanisms of PTE remain under debate. Using real-time time-dependent density functional theory (rt-TDDFT), we investigate ultrafast carrier thermalization in two-dimensional (2D) materials graphene and PtTe$_{2}$, and the results reveal distinct differences. In graphene, both electrons and holes thermalize into Fermi-Dirac distributions with good agreement to experiment, while PtTe$_{2}$ exhibits anomalous high-energy tails for both electrons and holes, deviating significantly from Fermi-Dirac behavior. We attribute this anomaly to differences in orbital coupling between the two materials, from which we derive design principles for identifying optimal PTE candidates and, ultimately, improving photodetector performance.

Key words: ultrafast phenomena, time-dependent density functional theory, photoelectronics, photo-thermionic emission, 2D materials, graphene, platinum ditelluride

中图分类号:  (Density functional theory, local density approximation, gradient and other corrections)

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87.15.ht (Ultrafast dynamics; charge transfer)