Peng Ruoming, Ripin Adina, Ye Yusen, Zhu Jiayi, Wu Changming, Lee Seokhyeong, Li Huan, Taniguchi Takashi, Watanabe Kenji, Cao Ting, Xu Xiaodong, Li Mo
Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, 98195, USA.
Department of Physics, University of Washington, Seattle, WA, 98195, USA.
Nat Commun. 2022 Mar 14;13(1):1334. doi: 10.1038/s41467-022-29042-9.
Excitons are elementary optical excitation in semiconductors. The ability to manipulate and transport these quasiparticles would enable excitonic circuits and devices for quantum photonic technologies. Recently, interlayer excitons in 2D semiconductors have emerged as a promising candidate for engineering excitonic devices due to their long lifetime, large exciton binding energy, and gate tunability. However, the charge-neutral nature of the excitons leads to weak response to the in-plane electric field and thus inhibits transport beyond the diffusion length. Here, we demonstrate the directional transport of interlayer excitons in bilayer WSe driven by the propagating potential traps induced by surface acoustic waves (SAW). We show that at 100 K, the SAW-driven excitonic transport is activated above a threshold acoustic power and reaches 20 μm, a distance at least ten times longer than the diffusion length and only limited by the device size. Temperature-dependent measurement reveals the transition from the diffusion-limited regime at low temperature to the acoustic field-driven regime at elevated temperature. Our work shows that acoustic waves are an effective, contact-free means to control exciton dynamics and transport, promising for realizing 2D materials-based excitonic devices such as exciton transistors, switches, and transducers up to room temperature.
激子是半导体中的基本光学激发。对这些准粒子进行操纵和传输的能力将使量子光子技术中的激子电路和器件成为可能。最近，二维半导体中的层间激子因其长寿命、大激子结合能和栅极可调性，已成为工程激子器件的一个有前途的候选者。然而，激子的电荷中性导致其对平面内电场的响应较弱，从而抑制了超过扩散长度的传输。在此，我们展示了在表面声波（SAW）诱导的传播势阱驱动下，双层WSe中层间激子的定向传输。我们表明，在100 K时，SAW驱动的激子传输在阈值声功率以上被激活，传输距离达到20μm，这一距离至少比扩散长度长十倍，且仅受器件尺寸限制。温度相关测量揭示了从低温下的扩散限制 regime 到高温下的声场驱动 regime 的转变。我们的工作表明，声波是控制激子动力学和传输的一种有效、无接触的手段，有望实现基于二维材料的激子器件，如激子晶体管、开关和换能器，直至室温。
