Excitons are composite bosons made of bound electron-hole pairs in semiconductors. With a much smaller mass than atoms, they are expected to Bose-condense at much higher temperature scales. This is especially the case for the tightly bound excitons in two-dimensional (2D) semiconductors; theoretical studies have predicted the possibility of realizing exciton superfluidity near room temperature. In this talk, I will discuss our recent efforts in creating a high-density equilibrium exciton fluid in atomic double layers made of 2D semiconductors. I will present results from both thermodynamics and transport measurements that help establish the emergence of a high-temperature excitonic insulating state. If time permits, I will also discuss the physics of a doped excitonic insulator that can support a Bose-Fermi mixture and an equilibrium trion fluid.

Our research group explores new physical phenomena in atomically thin materials and their heterostructures. We study a wide range of materials with very different properties, which include semiconductors, superconductors and magnets etc. We stack them together to form heteostructures and make electronics and opto-mechanical devices based on this material platform. To explore new phenomena, we also develop new measurement and imaging techniques suitable for specific problems on hand. Our ultimate goal is to push the limit on what can be seen and done in this two-dimensional world.