Acoustic Landau quantization and quantum-Hall-like edge states

Many intriguing phenomena occur for electrons under strong magnetic fields1,2. Recently, it was shown that an appropriate strain texture in graphene could induce a synthetic gauge field3–6, in which electrons behave as they do in a real magnetic field7–11. This enabled the control of quantum transport by mechanical means and allowed the unreached high-field regime to be explored. Such synthetic gauge fields have been achieved in molecular12 and photonic13 lattices. Here we report an experimental realization of a giant uniform pseudomagnetic field in acoustics by introducing a simple uniaxial deformation to the acoustic graphene. The controllability of our macroscopic platform enables us to observe the acoustic Landau levels in frequency-resolved spectroscopy and their spatial localization in pressure-field distributions. We further visualize the quantum-Hall-like edge states (connected to the zeroth Landau level), which have been elusive owing to the difficulty in creating large-area uniform pseudomagnetic fields5,6. These results, consistent with our full-wave simulations, establish a complete framework for artificial structures under constant pseudomagnetic fields. Our findings may also offer opportunities to manipulate sound in conceptually novel ways. A graphene-like two-dimensional sonic crystal, under uniaxial deformation, experiences a giant uniform pseudomagnetic field. This leads to the quantization of the cyclotron orbits—a kind of acoustic Landau level—that is observed here.