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Beveik nulinio indekso metamedžiagos iliustracija rodo, kad kai šviesa sklinda, ji juda pastovia faze. Kreditas: „Second Bay Studios“ / „Harvard SEAS“.
Nulinio indekso metamedžiagos suteikia naujų įžvalgų apie kvantinės mechanikos pagrindus.
Fizikoje, kaip ir gyvenime, visada gera į dalykus pažvelgti iš skirtingų perspektyvų.
Nuo kvantinės fizikos aušros, kaip šviesa juda ir sąveikauja su ją supančia medžiaga, pirmiausia buvo aprašyta ir suprantama matematiškai per jos energijos objektyvą. Maxas Planckas panaudojo energiją, kad paaiškintų, kaip šviesą skleidžia šildomi objektai 1900 m. – tai esminis kvantinės mechanikos pagrindų tyrimas. Albertas Einšteinas panaudojo energiją, kai 1905 m. pristatė fotono koncepciją.
Tačiau šviesa turi kitą, ne mažiau svarbią savybę, vadinamą impulsu. Ir, kaip paaiškėja, kai atimti pagreitį, šviesa pradeda elgtis tikrai įdomiai.
Tarptautinė fizikų komanda iš naujo nagrinėja kvantinės fizikos pagrindus iš impulso perspektyvos ir tiria, kas nutinka, kai šviesos impulsas sumažėja iki nulio. Mokslininkams vadovauja Michaël Lobet, Harvardo Johno A. Paulsono inžinerijos ir taikomųjų mokslų mokyklos (SEAS) mokslinis bendradarbis ir Ericas Mazuras, Balkanų fizikos ir taikomosios fizikos profesorius SEAS.
Tyrimas buvo paskelbtas žurnale Gamtos šviesos mokslas ir taikymas 2022 m. balandžio 25 d.
Bet kuris objektas, turintis masę ir greitį, turi impulsą – nuo atomų iki kulkų iki asteroidų – ir impulsą galima perkelti iš vieno objekto į kitą. Pistoletas atsitraukia, kai iššaunama kulka, nes kulkos impulsas perkeliamas į ginklą. Mikroskopiniu mastu, an[{” attribute=””>atom recoils when it emits light because of the acquired momentum of the photon. Atomic recoil, first described by Einstein when he was writing the quantum theory of radiation, is a fundamental phenomenon that governs light emission.
But a century after Planck and Einstein, a new class of metamaterials is raising questions regarding these fundamental phenomena. These metamaterials have a refractive index close to zero, meaning that when light travels through them, it doesn’t travel like a wave in phases of crests and troughs. Instead, the wave is stretched out to infinity, creating a constant phase. When that happens, many of the typical processes of quantum mechanics disappear, including atomic recoil.
Why? It all goes back to momentum. In these so-called near-zero index materials, the wave momentum of light becomes zero and when the wave momentum is zero, odd things happen.
“As physicists, it’s a dream to follow in the footsteps of giants like Einstein and push their ideas further. We hope that we can provide a new tool that physicists can use and a new perspective, which might help us understand these fundamental processes and develop new applications.”
— Michaël Lobet, Research Associate, SEAS
“Fundamental radiative processes are inhibited in three dimensional near-zero index materials,” says Lobet, who is currently a lecturer at the University of Namur in Belgium. “We realized that the momentum recoil of an atom is forbidden in near-zero index materials and that no momentum transfer is allowed between the electromagnetic field and the atom.”
If breaking one of Einstein’s rules wasn’t enough, the researchers also broke perhaps the most well-known experiment in quantum physics — Young’s double-slit experiment. This experiment is used in classrooms across the globe to demonstrate the particle-wave duality in quantum physics — showing that light can display characteristics of both waves and particles.
In a typical material, light passing through two slits produces two coherent sources of waves that interfere to form a bright spot in the center of the screen with a pattern of light and dark fringes on either side, known as diffraction fringes.
In the double slit experiment, light passing through two slits produces two coherent sources of waves that interfere to form a bright spot in the center of the screen with a pattern of light and dark fringes on either side, known as diffraction fringes. Credit: Harvard John A. Paulson School of Engineering and Applied Sciences
“When we modeled and numerically computed Young’s double-slit experiment, it turned out that the diffraction fringes vanished when the refractive index was lowered,” said co-author Larissa Vertchenko, of the Technical University of Denmark.
“As it can be seen, this work interrogates fundamental laws of quantum mechanics and probes the limits of wave-corpuscle duality,” said co-author Iñigo Liberal, of the Public University of Navarre in Pamplona, Spain.
While some fundamental processes are inhibited in near-zero refractive index materials, others are enhanced. Take another famous quantum phenomenon — Heisenberg’s uncertainty principle, more accurately known in physics as the Heisenberg inequality. This principle states that you cannot know both the position and speed of a particle with perfect
“These new theoretical results shed new light on near-zero refractive index photonics from a momentum perspective,” said Mazur. “It provides insights into the understanding of light-matter interactions in systems with a low- refraction index, which can be useful for lasing and quantum optics applications.”
The research could also shed light on other applications, including
Reference: “Momentum considerations inside near-zero index materials” by Michaël Lobet, Iñigo Liberal, Larissa Vertchenko, Andrei V. Lavrinenko, Nader Engheta and Eric Mazur, 25 April 2022, Light: Science & Applications.
DOI: 10.1038/s41377-022-00790-z