Nonlinear transport enabled by symmetry breaking in quantum materials has aroused considerable interest in condensed matter physics and interdisciplinary electronics. However, the nonlinear optical response in centrosymmetric Dirac semimetals via the defect engineering has remained highly challenging. Here, we observe the helicity-dependent terahertz (THz) emission in Dirac semimetal PtTe2 thin films via circular photogalvanic effect (CPGE) under normal incidence. This is activated by artificially controllable out-of-plane Te-vacancy defect gradient, which is unambiguously evidenced by the electron ptychography. The defect gradient lowers the symmetry, which not only induces the band spin splitting, but also generates the giant Berry curvature dipole (BCD) responsible for the CPGE. Such BCD-induced helicity-dependent THz emission can be manipulated by the Te-vacancy defect concentration. Furthermore, temperature evolution of the THz emission features the minimum of the THz amplitude due to the carrier compensation. Our work provides a universal strategy for symmetry breaking in centrosymmetric Dirac materials for efficient nonlinear transport and facilitates the promising device applications in integrated optoelectronics and spintronics.
@article{arxiv.2310.09989,
title = {Defect-induced helicity-dependent terahertz emission in Dirac semimetal PtTe2 thin films},
author = {Zhongqiang Chen and Hongsong Qiu and Xinjuan Cheng and Jizhe Cui and Zuanming Jin and Da Tian and Xu Zhang and Kankan Xu and Ruxin Liu and Wei Niu and Liqi Zhou and Tianyu Qiu and Yequan Chen and Caihong Zhang and Xiaoxiang Xi and Fengqi Song and Rong Yu and Xuechao Zhai and Biaobing Jin and Rong Zhang and Xuefeng Wang},
journal= {arXiv preprint arXiv:2310.09989},
year = {2024}
}