Ultrafast magnetization enhancement via the dynamic spin-filter effect of type-II Weyl nodes in a kagome ferromagnet

Xianyang Lu; Zhiyong Lin; Hanqi Pi; Tan Zhang; Guanqi Li; Yuting Gong; Yu Yan; Xuezhong Ruan; Yao Li; Hui Zhang; Lin Li; Liang He; Jing Wu; Rong Zhang; Hongming Weng; Changgan Zeng; Yongbing Xu

doi:10.1038/s41467-024-46604-1

Ultrafast magnetization enhancement via the dynamic spin-filter effect of type-II Weyl nodes in a kagome ferromagnet

Nat Commun. 2024 Mar 18;15(1):2410. doi: 10.1038/s41467-024-46604-1.

Authors

Xianyang Lu^#^{1

2

3}, Zhiyong Lin^#^{4

5}, Hanqi Pi^#^{6

7

8}, Tan Zhang⁹, Guanqi Li¹⁰, Yuting Gong^{2

3}, Yu Yan^{2

3}, Xuezhong Ruan^{2

3}, Yao Li^{2

3}, Hui Zhang^{4

5}, Lin Li^{4

5}, Liang He^{2

3}, Jing Wu^{11

12}, Rong Zhang³, Hongming Weng^{13

14

15}, Changgan Zeng^{16

17}, Yongbing Xu^{18

19

20

21}

Affiliations

¹ School of Integrated Circuits, Nanjing University, Suzhou, 215163, China.
² State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China.
³ Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China.
⁴ International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
⁵ CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
⁶ Beijing National Research Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
⁷ School of Physical Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
⁸ Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
⁹ Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19104-6323, USA.
¹⁰ School of Integrated Circuits, Guangdong University of Technology, Guangzhou, 510006, China.
¹¹ School of Integrated Circuits, Guangdong University of Technology, Guangzhou, 510006, China. jing.wu@gdut.edu.cn.
¹² York-Nanjing International Joint Center in Spintronics, School of Physics, Engineering and Technology, University of York, York, YO10 5DD, UK. jing.wu@gdut.edu.cn.
¹³ Beijing National Research Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. hmweng@iphy.ac.cn.
¹⁴ School of Physical Science, University of Chinese Academy of Sciences, Beijing, 100049, China. hmweng@iphy.ac.cn.
¹⁵ Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China. hmweng@iphy.ac.cn.
¹⁶ International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China. cgzeng@ustc.edu.cn.
¹⁷ CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China. cgzeng@ustc.edu.cn.
¹⁸ School of Integrated Circuits, Nanjing University, Suzhou, 215163, China. ybxu@nju.edu.cn.
¹⁹ State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China. ybxu@nju.edu.cn.
²⁰ Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China. ybxu@nju.edu.cn.
²¹ York-Nanjing International Joint Center in Spintronics, School of Physics, Engineering and Technology, University of York, York, YO10 5DD, UK. ybxu@nju.edu.cn.

^# Contributed equally.

Abstract

The magnetic type-II Weyl semimetal (MWSM) Co₃Sn₂S₂ has recently been found to host a variety of remarkable phenomena including surface Fermi-arcs, giant anomalous Hall effect, and negative flat band magnetism. However, the dynamic magnetic properties remain relatively unexplored. Here, we investigate the ultrafast spin dynamics of Co₃Sn₂S₂ crystal using time-resolved magneto-optical Kerr effect and reflectivity spectroscopies. We observe a transient magnetization behavior, consisting of spin-flipping dominated fast demagnetization, slow demagnetization due to overall half-metallic electronic structures, and an unexpected ultrafast magnetization enhancement lasting hundreds of picoseconds upon femtosecond laser excitation. By combining temperature-, pump fluence-, and pump polarization-dependent measurements, we unambiguously demonstrate the correlation between the ultrafast magnetization enhancement and the Weyl nodes. Our theoretical modelling suggests that the excited electrons are spin-polarized when relaxing, leading to the enhanced spin-up density of states near the Fermi level and the consequently unusual magnetization enhancement. Our results reveal the unique role of the Weyl properties of Co₃Sn₂S₂ in femtosecond laser-induced spin dynamics.

Abstract

Grants and funding