Visualizing Many Body Quantum States in Magical Flat Bands

The emergence of strongly correlated insulating, superconducting, and topological electronic phases at partial filling of the flat bands of magic angle bilayer graphene (MATBG) has been the subject of intense reserach in condensed matter physics. There are many theorethical proposals for the nature of correlated insulating phases, such as various broken symmetry phases involving spin or valley degree of freedom. The relation between these proposed phases and the emergence of superconductivity in this system remains also to be understood.Recently, we have demonstrated the power spectroscopic mapping with the STM in detecting broken symmetry phases and their topological excitations in Landau levels of monolayer graphene using the scanning tunneling microscope (STM).[1] The zeroth Landau level of graphene supports a variety of novel valley and spin polarized/coherent phases that can be directly visualized with the STM. Application of such visualization techniques to MATBG provides a powerful new tool to experimentally detect broken symmetry phases and to enable identification of the ground states in this system as function of filling. [2] I will present high-resolution low temperture STM spectrocoic maps of MATBG as function of partial filiing of its flat band and analyize them in the context of various proposed ground states for this system.