Acoustic Landau levels in a synthetic magnetic field with a symmetric gauge

Pseudomagnetic fields are promising for manipulating classical waves, including optic, acoustic, and elastic waves. One fascinating phenomenon is the presence of Landau energy levels and the involved quantum Hall effect, which are usually considered to exist only in quantum systems. Unlike using synthetic Landau gauge fields, as in existing works, here we successfully create a symmetric gauge field to achieve a large-area uniform pseudomagnetic field in a two-dimensional phononic crystal by introducing linear variations in the single-cell parameters of the scatterer along both the x and y directions. Discrete Landau levels are generated near the Dirac cone region, and the unidirectional propagation of acoustic waves along the domain wall, i.e., quantum Hall transport, is observed in experiment. The proposed structure offers greater flexibility by allowing free choice of the effective vector potential. Our study expands the application perspective of artificial acoustic devices that rely on a pseudomagnetic field.