2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/157809Linearly polarized light tuned slightly below the optical transition of the negatively charged exciton (trion) in a single quantum dot causes the spontaneous nuclear spin polarization (self-polarization) at a level close to 100%. The effective magnetic field of spin-polarized nuclei brings the optical transition energy into resonance with photon energy. The resonantly enhanced Overhauser effect sustains the stability of the nuclear self-polarization even in the absence of spin polarization of the quantum dot electron. As a result the optically selected single quantum dot represents a tiny magnet with the ferromagnetic ordering of nuclear spins - the nuclear spin nanomagnet.19 pages, including 3 figures. Short version has been accepted for publication in Physical Review LettersMesoscale and Nanoscale Physicstext