Acoustic analogue of graphene: observation of Dirac cones in acoustic surface waves

We demonstrate the presence of Dirac cones in the dispersion relation of acoustic waves propagating on the surface of a plate of methyl methacrylate containing a honeycomb lattice of cylindrical boreholes. This structure represents the acoustic analogue of graphene, the cylindrical cavities playing the role of carbon atoms while acoustic surface waves are the equivalent of electronic waves in graphene. Analytical expressions for the Dirac frequency and Dirac velocity in acoustics are given as a function of the radius and depth of boreholes. These parameters have been experimentally determined for a constructed structure and the data are in fairly good agreement with the predicted values. © 2012 American Physical Society.
Work supported by the Spanish Ministry of Science and Innovation (MICINN) under Contracts No. TEC2010-19751 and No. CSD2008-66 (CONSOLIDER program). Daniel Torrent acknowledges support from the program "Campus de Excelencia Internacional 2010 UPV." Both authors thank Didier Mayou for useful discussions.