Real-space observation of quantum Hall effect using exciton microscopy

An exciton is a quasiparticle composed of an electron and a hole bound by Coulomb interactions. These hydrogenic quasiparticles emit very narrow-spectrum light. The properties of the emitted light, such as polarization, photon energy, and intensity, can be utilized to achieve sensitive measurements of the space surrounding an exciton. Combination of exciton spectroscopy with microscopy enables the real-space imaging of such properties achieving spin-resolved high-energy-resolution spectroscopy. In this review paper, we unveil the versatile spatial patterns created by genuine fractional quantum Hall (FQH) effects. This technique can shed new light on a diverse range of systems beyond those exhibiting FQH effects. Thus, this technique is a powerful tool for probing the microscopic nature of many systems that are not well understood.