Direct Imaging of Quantum Scars in a Stadium-shaped Graphene Quantum Dot*

Wavefunction scarring (or quantum scars) refers to the enhancement of quantum probability density in the vicinity of classical periodic orbits of a chaotic system, which is a fundamental phenomenon connecting quantum and classical mechanics. Quantum scars are not only appealing to fundamental physics but also crucial for understanding the behavior of nanodevices, such as the conductance fluctuations of open quantum dots. More recently, the many-body version of quantum scars observed in atomic chains have also demonstrated their potential importance in quantum information. Quantum scars were first predicted to exist in stadium-shaped quantum billiards (a canonical chaotic system in classical mechanics) about 40 years ago, which has spurred extensive experimental attempts to image such states since then. Although clear scarred wavefunctions have been visualized in analog experiments such as microwave cavity experiments, unambiguous direct imaging of such states is still lacking in a real quantum system. In this talk, I will show our recent experimental progress on direct imaging of quantum scars in an electrostatically defined stadium-shaped graphene quantum dot with a low-temperature scanning tunneling microscope.