Topological Dirac nodal-line semimetals host topologically nontrivial electronic structure with nodal-line crossings around the Fermi level, which could affect the photocarrier dynamics and lead to novel relaxation mechanisms. Herein, by using time- and angle-resolved photoemission spectroscopy, we reveal the previously-inaccessible linear dispersions of the bulk conduction bands above the Fermi level in a Dirac nodal-line semimetal PtSn4, as well as the momentum and temporal evolution of the gapless nodal lines. A surprisingly ultrafast relaxation dynamics within a few hundred femtoseconds is revealed for photoexcited carriers in the nodal line. Theoretical calculations suggest that such ultrafast carrier relaxation is attributed to the multichannel scatterings among the complex metallic bands of PtSn4 via electron-phonon coupling. In addition, a unique dynamic relaxation mechanism contributed by the highly anisotropic Dirac nodal-line electronic structure is also identified. Our work provides a comprehensive understanding of the ultrafast carrier dynamics in a Dirac nodal-line semimetal.
@article{arxiv.2405.11901,
title = {Ultrafast Carrier Relaxation Dynamics in a Nodal-Line Semimetal PtSn$_4$},
author = {Tianyun Lin and Yongkang Ju and Haoyuan Zhong and Xiangyu Zeng and Xue Dong and Changhua Bao and Hongyun Zhang and Tian-Long Xia and Peizhe Tang and Shuyun Zhou},
journal= {arXiv preprint arXiv:2405.11901},
year = {2024}
}