Metalenses for Ballistic Electrons: Toward Room-Temperature Electron Optics

Quantum electron optics offers a promising route to transistors that manipulate ballistic electrons analogously to light. A key goal is a lens with full capabilities of focusing, imaging, and collimation, yet such a device has not been demonstrated in two-dimensional ballistic materials, limiting the realization of amplifiers for microscopic imaging and couplers or collimators in electrical circuits. Here, we theoretically realize a graphene metalens for ballistic electrons, implemented as a linear array of quantum dots. The design combines miniaturization, freedom from spherical aberration, subwavelength-resolution imaging, and near-perfect efficiency. Remarkably, the lens, compressed into a line, has a thickness far smaller than the room-temperature ballistic transport distance, enabling practical operation under ambient conditions. This work highlights emerging opportunities in quantum electron optics to create transistors capable of room-temperature operation.