Ultrathin quantum light source with van der Waals NbOCl2 crystal

Qiangbing Guo; Xiao-Zhuo Qi; Lishu Zhang; Meng Gao; Sanlue Hu; Wenju Zhou; Wenjie Zang; Xiaoxu Zhao; Junyong Wang; Bingmin Yan; Mingquan Xu; Yun-Kun Wu; Goki Eda; Zewen Xiao; Shengyuan A Yang; Huiyang Gou; Yuan Ping Feng; Guang-Can Guo; Wu Zhou; Xi-Feng Ren; Cheng-Wei Qiu; Stephen J Pennycook; Andrew T S Wee

doi:10.1038/s41586-022-05393-7

Ultrathin quantum light source with van der Waals NbOCl₂ crystal

Nature. 2023 Jan;613(7942):53-59. doi: 10.1038/s41586-022-05393-7. Epub 2023 Jan 4.

Authors

Qiangbing Guo^#^{1

2

3}, Xiao-Zhuo Qi^#^{4

5}, Lishu Zhang^#⁶, Meng Gao^#⁷, Sanlue Hu⁸, Wenju Zhou⁹, Wenjie Zang¹⁰, Xiaoxu Zhao¹¹, Junyong Wang^{12

6}, Bingmin Yan⁹, Mingquan Xu⁷, Yun-Kun Wu^{4

5}, Goki Eda^{12

6}, Zewen Xiao⁸, Shengyuan A Yang¹³, Huiyang Gou⁹, Yuan Ping Feng^{12

6}, Guang-Can Guo^{4

5

14}, Wu Zhou^{7

15}, Xi-Feng Ren^{16

17

18}, Cheng-Wei Qiu^{19

20}, Stephen J Pennycook^{21

22}, Andrew T S Wee^{23

24}

Affiliations

¹ Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore. qbguo90@hotmail.com.
² Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore. qbguo90@hotmail.com.
³ Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore. qbguo90@hotmail.com.
⁴ CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, China.
⁵ CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, China.
⁶ Department of Physics, National University of Singapore, Singapore, Singapore.
⁷ School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, China.
⁸ Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, China.
⁹ Center for High Pressure Science and Technology Advanced Research, Beijing, China.
¹⁰ Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore.
¹¹ School of Materials Science and Engineering, Peking University, Beijing, China.
¹² Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore.
¹³ Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, Singapore.
¹⁴ Hefei National Laboratory, University of Science and Technology of China, Hefei, China.
¹⁵ CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China.
¹⁶ CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, China. renxf@ustc.edu.cn.
¹⁷ CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, China. renxf@ustc.edu.cn.
¹⁸ Hefei National Laboratory, University of Science and Technology of China, Hefei, China. renxf@ustc.edu.cn.
¹⁹ Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore. chengwei.qiu@nus.edu.sg.
²⁰ Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore. chengwei.qiu@nus.edu.sg.
²¹ Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore. stephen.pennycook@cantab.net.
²² School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, China. stephen.pennycook@cantab.net.
²³ Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore. phyweets@nus.edu.sg.
²⁴ Department of Physics, National University of Singapore, Singapore, Singapore. phyweets@nus.edu.sg.

^# Contributed equally.

PMID: 36600061
DOI: 10.1038/s41586-022-05393-7

Abstract

Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl₂), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS₂. Notably, the strong second-order nonlinearity enables correlated parametric photon pair generation, through a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as about 46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in two-dimensional layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources as well as high-performance photon modulators in both classical and quantum optical technologies^1-4.

Publication types

Research Support, Non-U.S. Gov't