The intricate competition between coexisting charge density waves (CDWs) can lead to rich phenomena, offering unique opportunities for phase manipulation through electromagnetic stimuli. Leveraging time-resolved X-ray diffraction, we demonstrate ultrafast control of a CDW in EuTe4 upon optical excitation. At low excitation intensities, the amplitude of one of the coexisting CDW orders increases at the expense of the competing CDW, whereas at high intensities, it exhibits a nonmonotonic temporal evolution characterized by both enhancement and reduction. This transient bidirectional controllability, tunable by adjusting photo-excitation intensity, arises from the interplay between optical quenching and phase-competition-induced enhancement. Our findings, supported by phenomenological time-dependent Ginzburg-Landau theory simulations, not only clarify the relationship between the two CDWs in EuTe4, but also highlight the versatility of optical control over order parameters enabled by phase competition.
@article{arxiv.2510.00204,
title = {Bidirectional ultrafast control of charge density waves via phase competition},
author = {Honglie Ning and Kyoung Hun Oh and Yifan Su and Zhengyan Darius Shi and Dong Wu and Qiaomei Liu and B. Q. Lv and Alfred Zong and Gyeongbo Kang and Hyeongi Choi and Hyun-Woo J. Kim and Seunghyeok Ha and Jaehwon Kim and Suchismita Sarker and Jacob P. C. Ruff and B. J. Kim and N. L. Wang and Todadri Senthil and Hoyoung Jang and Nuh Gedik},
journal= {arXiv preprint arXiv:2510.00204},
year = {2025}
}