Giant permanent dipole moment of two-dimensional excitons bound to a single stacking fault

Two-dimensional potentials are excellent test beds for the physics of interacting excitonic gases, but engineering highly homogeneous potentials can be challenging. In this work, the authors investigate excitons bound to a single 10-\ensuremath{\mu}m scale stacking fault, finding excitonic luminescence with unprecedented homogeneity. The authors further show that stacking-fault-bound excitons are mobile and have a giant permanent dipole moment by means of the magneto-Stark effect. These results indicate that stacking faults may be a promising platform to probe the many-body physics of interacting dipoles in an atomically smooth potential.