Kumar Abhijeet M, Yagodkin Denis, Rosati Roberto, Bock Douglas J, Schattauer Christoph, Tobisch Sarah, Hagel Joakim, Höfer Bianca, Kirchhof Jan N, Hernández López Pablo, Burfeindt Kenneth, Heeg Sebastian, Gahl Cornelius, Libisch Florian, Malic Ermin, Bolotin Kirill I
Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany.
Philipps-Universität Marburg, Mainzer Gasse 33, Marburg, Germany.
Nat Commun. 2024 Aug 30;15(1):7546. doi: 10.1038/s41467-024-51195-y.
Intervalley excitons with electron and hole wavefunctions residing in different valleys determine the long-range transport and dynamics observed in many semiconductors. However, these excitons with vanishing oscillator strength do not directly couple to light and, hence, remain largely unstudied. Here, we develop a simple nanomechanical technique to control the energy hierarchy of valleys via their contrasting response to mechanical strain. We use our technique to discover previously inaccessible intervalley excitons associated with K, Γ, or Q valleys in prototypical 2D semiconductors WSe and WS. We also demonstrate a new brightening mechanism, rendering an otherwise "dark" intervalley exciton visible via strain-controlled hybridization with an intravalley exciton. Moreover, we classify various localized excitons from their distinct strain response and achieve large tuning of their energy. Overall, our valley engineering approach establishes a new way to identify intervalley excitons and control their interactions in a diverse class of 2D systems.
电子和空穴波函数位于不同能谷的谷间激子决定了在许多半导体中观察到的长程输运和动力学。然而，这些振子强度消失的激子并不直接与光耦合，因此在很大程度上仍未得到研究。在这里，我们开发了一种简单的纳米机械技术，通过谷对机械应变的对比响应来控制能谷的能量层级。我们利用该技术发现了与典型二维半导体WSe₂和WS₂中的K、Γ或Q能谷相关的、以前无法获得的谷间激子。我们还展示了一种新的亮化机制，通过与谷内激子的应变控制杂化，使原本“暗”的谷间激子变得可见。此外，我们根据各种局域激子不同的应变响应进行分类，并实现了它们能量的大幅调谐。总体而言，我们的能谷工程方法为识别谷间激子并控制它们在各种二维系统中的相互作用建立了一种新途径。
