Direct observation of Landau Levels in artificial strained graphene

We study the steady state of out-of-equilibrium artificial graphene in the presence
of unidirectional strain. We demonstrate that the equilibrium energy spectra of such
a system exhibits Landau levels, and we calculate the analytical eigenspectrum
around the Dirac cones. We find deviations from the usual flat Landau levels due to
a space-dependent Fermi velocity. We also describe how to probe the Landau level
spectra in the steady state of a lossy, coherently-pumped system like, for instance,
a photonic lattice made of coupled micropillars arranged in a honeycomb geometry. We
show that each eigenstate corresponds to a peak in the frequency spectra so that, on
resonance with that peak, the spatial field amplitude distribution follows the
wavefunction of that mode. These features could be measured directly in experiments
and would be a clear validation of the Landau level description.