  Strong electronic correlations can produce remarkable phenomena such as
metal-insulator transitions and greatly enhance superconductivity,
thermoelectricity, or optical non-linearity. In correlated systems, spatially
varying charge textures also amplify magnetoelectric effects or
electroresistance in mesostructures. However, how spatially varying spin
textures may influence electron transport in the presence of correlations
remains unclear. Here we demonstrate a very large topological Hall effect (THE)
in thin films of a lightly electron-doped charge-transfer insulator, (Ca,
Ce)MnO3. Magnetic force microscopy reveals the presence of magnetic bubbles,
whose density vs. magnetic field peaks near the THE maximum, as is expected to
occur in skyrmion systems. The THE critically depends on carrier concentration
and diverges at low doping, near the metal-insulator transition. We discuss the
strong amplification of the THE by correlation effects and give perspectives
for its non-volatile control by electric fields.
