  We provide a microscopic theory for semiconductor quantum dots that explains
the pronounced deviations from the prevalent point-dipole description that were
recently observed in spectroscopic experiments on quantum dots in photonic
nanostructures. At the microscopic level the deviations originate from
structural inhomogeneities generating a large circular quantum current density
that flows inside the quantum dot over mesoscopic length scales. The model is
supported by the experimental data, where a strong variation of the multipolar
moments across the emission spectrum of quantum dots is observed. Our work
enriches the physical understanding of quantum dots and is of significance for
the fields of nanophotonics, quantum photonics, and quantum-information
science, where quantum dots are actively employed.
