Light Control of Charge Transport and Phase Transitions

Photoexcitation is a powerful means in distinguishing different interactions and manipulating the properties of matter, especially for charge transport and phase transitions in complex quantum systems.<br/>Here we show that laser-controlled coherent phonon excitation enables orders of magnitude enhancement of carrier mobility via accelerating polaron transport in a prototypical material, lithium peroxide (Li2O2). The selective excitation of specific phonon modes, whose vibrational pattern directly overlap with the polaronic lattice deformation, can remarkably reduce the energy barrier for polaron hopping. The strong nonadiabatic couplings between the electronic and ionic subsystem play a key role in triggering charge transport. These results extend our understanding of charge transport dynamics to the nonequilibrium regime and allow for optoelectronic devices with ultrahigh on-off ratio and ultrafast responsibility competitive with those of state-of-the-art devices. We also investigate photoexcitation induced ultrafast phase-transition dynamics in two-dimensional materials, where we identify a laser-induced collective pathway from 2H phase to 1T phase in MoTe2 that is significantly different from thermal phase transitions. Our results provide insights from a new perspective on the coherent electron and lattice quantum dynamics in materials upon photoexcitation.<br/> <br/>References:<br/>H.M. Wang, X.B. Liu, S.Q. Hu, D.Q. Chen, Q. Chen, C. Zhang, M.X. Guan, S. Meng. Giant acceleration of polaron transport by ultrafast laser-induced coherent phonons. Science Advances 9, eadg3833 (2023).<br/>R.J. Zhao, P.W. You, S. Meng, Ring polymer molecular dynamics with electronic transitions, Phys. Rev. Lett. 130, 166401 (2023).<br/>C.Y. Wang, X.B. Liu, Q. Chen, D.Q. Chen, Y.X. Wang, S. Meng. Coherent-Phonon-Driven Intervalley Scattering and Rabi Oscillation in Multivalley 2D Materials. Phys. Rev. Lett. 131, 066401 (2023).<br/>M.X. Guan, X.B. Liu, D.Q. Chen, X.Y. Li, Y.P. Qi, Q. Yang, P.W. You, S. Meng. Optical control of multi-stage phase transition via phonon couplings in MoTe2. Phys. Rev. Lett. 128, 015702 (2022).<br/>J.Y. Xu, D.Q. Chen, S. Meng. Decoupled ultrafast electronic and structural phase transitions in photoexcited monoclinic VO2. Science Advances 8, eadd2392 (2022).