Perfect transmission through barrier using sound — ScienceDaily

A study crew led by Professor Xiang Zhang, President of the University of Hong Kong (HKU) when he was a professor at the University of California, Berkeley, (UC Berkeley) has for the very first time experimentally proved a century aged quantum theory that relativistic particles can move via a barrier with a hundred% transmission. The study results have been revealed in the prime tutorial journal Science.

Just as it would be tricky for us to jump in excess of a thick higher wall without having sufficient power gathered. In distinction, it is predicted that a microscopic particle in the quantum environment can move via a barrier well outside of its power irrespective of the peak or width of the barrier, as if it is “clear.”

As early as 1929, theoretical physicist Oscar Klein proposed that a relativistic particle can penetrate a probable barrier with a hundred% transmission upon ordinary incidence on the barrier. Scientists identified as this exotic and counterintuitive phenomenon the “Klein tunneling” theory. In the pursuing a hundred odd yrs, scientists tried out various ways to experimentally exam Klein tunneling, but the tries were unsuccessful and direct experimental proof is however missing.

Professor Zhang’s crew executed the experiment in artificially developed phononic crystals with triangular lattice. The lattice’s linear dispersion qualities make it feasible to mimic the relativistic Dirac quasiparticle by sound excitation, which led to the productive experimental observation of Klein tunneling.

“This is an exciting discovery. Quantum physicists have generally tried out to observe Klein tunneling in elementary particle experiments, but it is a really tricky undertaking. We developed a phononic crystal related to graphene that can excite the relativistic quasiparticles, but not like pure product of graphene, the geometry of the human-created phononic crystal can be altered freely to exactly reach the ideal problems that created it feasible to the very first direct observation of Klein tunneling,” mentioned Professor Zhang.

The achievement not only represents a breakthrough in essential physics, but also provides a new system for discovering emerging macroscale devices to be utilized in applications these kinds of as on-chip logic products for sound manipulation, acoustic signal processing, and sound power harvesting.

“In present acoustic communications, the transmission loss of acoustic power on the interface is unavoidable. If the transmittance on the interface can be improved to nearly a hundred%, the efficiency of acoustic communications can be significantly enhanced, as a result opening up chopping-edge applications. This is especially important when the floor or the interface participate in a job in hindering the precision acoustic detection these kinds of as underwater exploration. The experimental measurement is also conducive to the foreseeable future development of studying quasiparticles with topological assets in phononic crystals which could possibly be tricky to complete in other devices,” mentioned Dr. Xue Jiang, a previous member of Zhang’s crew and currently an Affiliate Researcher at the Section of Digital Engineering at Fudan University.

Dr. Jiang pointed out that the study results could possibly also reward the biomedical products. It might assistance to boost the precision of ultrasound penetration via obstacles and reach designated targets these kinds of as tissues or organs, which could boost the ultrasound precision for greater prognosis and remedy.

On the foundation of the present experiments, scientists can control the mass and dispersion of the quasiparticle by exciting the phononic crystals with unique frequencies, as a result accomplishing flexible experimental configuration and on/off control of Klein tunneling. This method can be prolonged to other artificial construction for the review of optics and thermotics. It allows the unprecedent control of quasiparticle or wavefront, and contributes to the exploration on other advanced quantum actual physical phenomena.

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