[NCTS Physics Research Highlights] Yang-hao Chan & Guang-Yu Guo 'Strongly enhanced shift current at exciton resonances in a noncentrosymmetric wide-gap semiconductor', Nature Comms. 15, 9672 (2024)

• 2024-12-09
• Chen, Jhan Yu 陳詹喻
• Computational quantum materials Condensed Matter

Strongly enhanced shift current at exciton resonances in a noncentrosymmetric wide-gap semiconductor
在非中心對稱寬帶隙半導體中激子共振時引發的強烈增強的位移電流

Masao Nakamura, Yang-Hao Chan*, Takahiro Yasunami, Yi-Shiuan Huang, Guang-Yu Guo*, Yajian Hu, Naoki Ogawa, Yiling Chiew, Xiuzhen Yu, Takahiro Morimoto, Naoto Nagaosa, Yoshinori Tokura & Masashi Kawasaki
Nature Communications volume 15, 9672 (2024)
DOI: https://doi.org/10.1038/s41467-024-53541-6

Excitons are ubiquitous in photoexcited semiconductors. Despite their strong photo-absorption, charge-neutral excitons do not yield photocurrent in conventional photovoltaic processes before dissociation. Together with experimentalists we demonstrate that excitons can directly contribute to photocurrent generation through a nonlinear optical response, known as shift current, in noncentrosymmetric semiconductor CuI. First-principles calculations elucidate that the sign and magnitude of the enhanced shift current at exciton resonance depend strongly on the strain in the thin film. The present study might provide an novel route for manipulation of shift current and better understanding of electron geometric Berry phase and excitonic effects.

激子是光激發半導體中普遍存在的基本準粒子。儘管電荷中性激子具有很強的光吸收作用，但在解離之前，它們在傳統的光伏過程中不會產生光電流。透過與實驗人員合作，我們證明激子可以透過非中心對稱半導體 CuI 中的非線性光學響應（稱為位移電流）直接促進光電流的產生。第一原理計算闡明了激子共振時增強的位移電流的符號和大小及其對薄膜應變的強烈依賴性。目前的研究可能會帶來前所未有的控制位移電流的途徑，並更好地理解電子幾何貝里相及激子效應間的交互作用。