We conduct photoluminescence microscopy that is sensitive to both electron and nuclear spin polarization to investigate the changes that occur in the magnetic ordering in the vicinity of the first integer quantum Hall state in a GaAs 2D electron system (2DES). We observe a discontinuity in the electron spin polarization and nuclear spin longitudinal relaxation time which heralds a spontaneous transition in the magnetic ordering. We image in real space the spin phase domains that coexist at this transition, and observe hysteresis in their formation as a function of the 2DES’s chemical potential. Based on measurements in a tilted magnetic field orientation, we found that
the transition is protected by an energy gap containing the Zeeman energy. We explain that these observations are consistent with a phase of skyrmions forming at the transition.

J. N. Moore et al., Phys. Rev. B 98, 161402(R) (2018).