We report on systematic investigation of hot carrier dynamics in Ti4O7 by ultrafast time-resolved optical reflectivity. We find the transient indication for its two-step insulator-metal (I-M) transition, in which two phase transitions occur from long-range order bipolaron low-temperature insulating (LI) phase to disordered bipolaron high-temperature insulating (HI) phase at Tc1 and to free carrier metallic (M) phase at Tc2. Our results reveal that photoexcitation can effectively lower down both Tc1 and Tc2 with pump fluence increasing, allowing a light-control of I-M transition. We address a phase diagram that provides a framework for the photoinduced I-M transition and helps the potential use of Ti4O7 for photoelectric and thermoelectric devices.
@article{arxiv.1805.06721,
title = {Photoinduced two-step insulator-metal transition in Ti4O7 by ultrafast time-resolved optical reflectivity},
author = {X. C. Nie and Hai-Ying Song and Xiu Zhang and Shi-Bing Liu and Fan Li and Lili Yue and Jian-Qiao Meng and Yu-Xia Duan and H. Y. Liu},
journal= {arXiv preprint arXiv:1805.06721},
year = {2018}
}