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    Cunzheng-NING, Hao-SUN and Qiyao-ZHANG et al. of the Department of Electronic Engineering discovered a new method to control electron spin-valley

    On July 14, the team of Professor Cunzheng-NING and associate researcher Hao-SUN from the Department of Electronic Engineering of Tsinghua University, published a research paper entitled “Prolonging valley polarization lifetime through gate-controlled exciton-to-trion conversion in monolayer molybdenum ditelluride” in Nature Communications. In this paper, it is proposed to change the main depolarization channels in the material through electrically-controlled exciton-to-trion conversion, thereby increasing the valley lifetime in monolayer molybdenum ditelluride (MoTe2) from picosecond by three orders of magnitude to nanosecond scale. In addition, valley polarization fluorescence of monolayer MoTe2 is observed for the first time in the absence of magnetic field, and the valley polarizability of exciton and trion is 38% and 33% respectively under electrical control. This work reveals the valley dynamics of excitons and trions and the interaction mechanism between various depolarization channels, providing an effective strategy for prolonging the valley polarization.

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