Intertwined orbital distribution of charge density waves in NbSe₂

Jyun-Yu Wu¹, Yung-Ting Lee^2,11*, Guan-Hao Chen^1,3, Zheng-Hong Li¹, Chang-Tsan Lee¹, Jie-Yu Hsu¹, Chia-Nung Kuo⁴, Juhn-Jong Lin¹, Wen-Hao Chang^1,3, Chin-Shan Lue^4,5, Noriaki Takagi⁶, Po-Tuan Chen², Cheng-Tien Chiang^7,8, Chien-Cheng Kuo⁹, Chien-Te Wu¹, Chi-Cheng Lee⁸, Ming-Chiang Chung¹⁰, Hung-Chung Hsueh⁸, Chun-Liang Lin¹

¹Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Vehicle Engineering, National Taipei University of Technology, Taipei, Taiwan
³Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
⁴Physics, National Cheng Kung University, Tainan, Taiwan
⁵Consortium of Emergent Crystalline Materials, National Science and Technology Council, Taipei, Taiwan
⁶Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
⁷Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
⁸Physics, Tamkang University, New Taipei City, Taiwan
⁹Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan
¹⁰Physics, National Chung Hsing University, Taichung, Taiwan
¹¹Department of Applied Science, National Taitung University, Taitung, Taiwan

* Presenter:Yung-Ting Lee, email:ytl@nttu.edu.tw

Charge density wave (CDW) resulting from a periodic distortion in the lattice creates new orders beyond the original lattice. In 2H-NbSe₂, one of the layered transition metal dichalcogenides (TMD), the 3x3 charge order appears in two-dimensional (2D) layers. Although CDW can be observed by different techniques, the spatial distribution within a 2D layer has never been systematically visualized. Here, by using scanning tunneling microscopy (STM) and density functional theory (DFT), we monitored the evolution of CDW along the c-axis and found a strong relation with the orbital charges. The results show that the appearance of the CDW varies while tuning the tunneling current and undergoes a transition from Se orbital charges to Nb orbital charges. The calculation of orbital charge distributions shows that both CDW intensity modulation and the transition are strongly intertwined with the distribution of Se 4p orbitals and Nb 4d orbitals.

Keywords: charge density wave, scanning tunneling microscopy, density functional theory, transition metal dichalcogenides