Nearfield scanning optical microscopy of dynamically twistable TMDs

The periodic potential generated in transition metal dichalcogenide (TMD) moiré superlattices can trap electrons and holes to form an array of optically active single emitters and other exotic quantum states. The twist angle in TMD moiré superlattices critically determines the properties of the superlattice potential and thereby the optical properties of the emitters. However, twisted devices are generally fabricated with a fixed angle that cannot be modified once the device has been made. In addition, the Moiré unit cell is below optical wavelengths, making it difficult to address single emitters with free-space optics. In this work, we develop a new platform for reliable creation and read-out of Moiré emitters. This platform combines two capabilities: 1) a "Twistronics" apparatus that can bring two van der Waals layers into direct contact and rotate them relative to each other which allows for precise in-situ control of interlayer twist angle. 2) a near-field scanning optical probe that can collect light from a subwavelength scale spot, making it possible to address single photon emitters in moiré superlattices. We discuss the merits and challenges of the design and report our progress in using it to study the optical properties of TMD heterolayers.