Chan Yang-Hao, Qiu Diana Y, da Jornada Felipe H, Louie Steven G
Department of Physics, University of California, Berkeley, CA 94720-7300.
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
Proc Natl Acad Sci U S A. 2021 Jun 22;118(25). doi: 10.1073/pnas.1906938118.
Shift current is a direct current generated from nonlinear light-matter interaction in a noncentrosymmetric crystal and is considered a promising candidate for next-generation photovoltaic devices. The mechanism for shift currents in real materials is, however, still not well understood, especially if electron-hole interactions are included. Here, we employ a first-principles interacting Green's-function approach on the Keldysh contour with real-time propagation to study photocurrents generated by nonlinear optical processes under continuous wave illumination in real materials. We demonstrate a strong direct current shift current at subbandgap excitation frequencies in monolayer GeS due to strongly bound excitons, as well as a giant excitonic enhancement in the shift current coefficients at above bandgap photon frequencies. Our results suggest that atomically thin two-dimensional materials may be promising building blocks for next-generation shift current devices.
转移电流是由非中心对称晶体中的非线性光-物质相互作用产生的直流电流，被认为是下一代光伏器件的一个有前途的候选者。然而，实际材料中转移电流的机制仍未得到很好的理解，特别是当考虑电子-空穴相互作用时。在这里，我们采用基于含时传播的Keldysh轮廓的第一性原理相互作用格林函数方法，来研究实际材料在连续波照明下由非线性光学过程产生的光电流。我们证明，由于强束缚激子的存在，单层GeS在亚带隙激发频率下有很强的直流转移电流，并且在带隙以上光子频率下转移电流系数有巨大的激子增强。我们的结果表明，原子级薄的二维材料可能是下一代转移电流器件的有前途的构建块。
