Electron-optics

The relativistic charge carriers in monolayer graphene can be manipulated in a manner akin to conventional optics. Klein tunneling and Veselago lensing have been previously demonstrated in ballistic graphene pn-junction devices, but the collimation and focusing efficiency remain relatively low, preventing the realization of advanced quantum devices and controlled quantum interference. In our group, we are exploring new device architectures with careful engineering of twist, local electrostatic and atomic strain to improve the collimation efficiency and to demonstrate new electron-optics quantum phenomena and device functionalities. These experiments shed new light on relativistic single-particle physics and provide new device components toward next-generation quantum electronics based on the manipulation of ballistic electron trajectories.

Selected Publications

Electro-Optics-2

Electron Collimation in Twisted Bilayer Graphene via Gate-Defined Moiré Barriers

Demonstrate collimation of the electron flow via gate-defined moiré barriers in a twisted bilayer graphene device.


Wei Ren, Xi Zhang, Ziyan Zhu, Moosa Khan, Kenji Watanabe, Takashi Taniguchi, Efthimios Kaxiras, Mitchell Luskin, Ke Wang, Nano Letters 40, 12508-12514 (2024)


 

Electro-Optics-1

Gate-tunable Veselago Interference in a Bipolar Graphene Microcavity

Present a graphene microcavity defined by carefully-engineered local strain and electrostatic fields to improve electron collimation.


Xi Zhang*, Wei Ren*, Elliot Bell, Ziyan Zhu, Kan-Ting Tsai, Yujie Luo, Kenji Watanabe, Takashi Taniguchi, Efthimios Kaxiras, Mitchell Luskin, Ke Wang, Nature Communications 13, 6711 (2022)
  
 

Graphene Transistor Based on Tunable Dirac Fermion Optics

Report an electrically tunable graphene quantum switch based on Dirac fermion optics, with electrostatically defined analogies of mirrors and collimators utilizing angle-dependent Klein tunneling.


K. Wang, M. M. Elahi, K. M. M. Habib, T. Taniguchi, K. Watanabe, A. W. Ghosh, G.-H. Lee, P. Kim, Proceedings of the National Academy of Science, 116 (14) 6575-6579 (2019)