Magnetically amplified light-shining-through-walls via virtual minicharged particles

We show that magnetic fields have the potential to significantly enhance a recently proposed light-shining-through-walls scenario in quantum-field theories with photons coupling to minicharged particles. Suggesting a dedicated laboratory experiment, we demonstrate that this particular tunneling scenario could provide access to a parameter regime competitive with the currently best direct laboratory limits on minicharged fermions below the $\mathrm{meV}$ regime. With present day technology, such an experiment has the potential to even overcome the best model-independent cosmological bounds on minicharged fermions with masses below $\mathcal{O} (10^{-4}) \mathrm{eV}$.