Manipulation of invisible cloaking in PT -symmetric thermoacoustic dimer

Making the propagation of sound waves immune to interference from obstacles with high transmission efficiency is a long-term pursuit in acoustic science and engineering. Recent proposal pointed out that perfect transmission through obstacles can be achieved by deploying a bulky gain-loss distribution in parity-time (PT) symmetry. Here we demonstrate a modified methodology to achieve the extraordinary physical property of acoustic cloaking accompanied by perfect transmission at the exceptional points (EPs). Systematically probing reveals two complementary solutions of EPs corresponding to acoustic cloaking, in the system composed of an equivalent medium slab sandwiched by a pair of PT -symmetric admittance metasurfaces. To model the crucial acoustic gains that are not present in nature, we employ actively controlled ultra-thin carbon nanotube dimer films to mimic admittance metasurfaces perfectly via thermoacoustic effect, and manipulate acoustic cloaking over a wide frequency band in experiments. This divergent strategy releases restrictions on the operating frequency, shape and size of the obstacle, which can be applied to acoustic sensing, directional imaging, and other related wave disciplines.