  Artificial magnetic fields are revolutionizing our ability to manipulate
neutral particles, by enabling the emulation of exotic phenomena once thought
to be exclusive to charged particles. In particular, pseudo-magnetic fields
generated by nonuniform strain in artificial lattices have attracted
considerable interest because of their simple geometrical origin. However, to
date, these strain-induced pseudo-magnetic fields have failed to emulate the
tunability of real magnetic fields because they are dictated solely by the
strain configuration. Here, we overcome this apparent limitation for polaritons
supported by strained metasurfaces, which can be realized with classical dipole
antennas or quantum dipole emitters. Without altering the strain configuration,
we unveil how one can tune the pseudo-magnetic field by modifying the
electromagnetic environment via an enclosing photonic cavity which modifies the
nature of the interactions between the dipoles. Remarkably, due to the
competition between short-range Coulomb interactions and long-range
photon-mediated interactions, we find that the pseudo-magnetic field can be
entirely switched off at a critical cavity height for any strain configuration.
Consequently, by varying only the cavity height, we demonstrate a tunable
Lorentz-like force that can be switched on/off and an unprecedented collapse
and revival of polariton Landau levels. Unlocking this tunable pseudo-magnetism
for the first time poses new intriguing questions beyond the paradigm of
conventional tight-binding physics.
