New research from a City College of New York team has revealed a new way to combine two different material states. For one of the first times, topological photons – light – have been combined with lattice vibrations, also known as phonons, to manipulate their propagation in a robust and controllable way.
The study used topological photonics, a prominent direction in photonics that exploits basic ideas in mathematical topology about conserved quantities – topological invariants – that remain constant when parts of a geometric object change during continuous deformations. One of the simplest examples of such invariants is the number of holes, such as Make donut and mug equivalent from the topological point of view. The topological properties give photons helicity when photons rotate as they multiply, leading to unique and unexpected properties, such as robustness against defects and unidirectional propagation along interfaces between topologically different materials. Thanks to interactions with vibrations in crystals, these helical photons can then be used to channel infrared light along with vibrations.
The implications of this work are broad, particularly allowing researchers to advance Raman spectroscopy, which is used to determine the vibrational states of molecules. The research also promises vibration spectroscopy – also known as infrared spectroscopy – which measures the interaction between infrared radiation and matter through absorption, emission or reflection. This can then be used to study and identify and characterize chemical substances.
“We coupled helical photons with lattice vibrations in hexagonal boron nitride and created a new hybrid substance referred to as phonon polaritons,” said Alexander Khanikaev, lead author and physicist affiliated with CCNY’s Grove School of Engineering. “It’s half light and half vibration. Since infrared light and lattice vibrations are associated with heat, we created new channels for the propagation of light and heat together. Typically, lattice vibrations are very difficult to control and direct them around defects and sharp corners were impossible before. “
The new method can also implement directional radiant heat transfer, a form of energy transfer during which heat is dissipated through electromagnetic waves.
“We can create channels of any shape for this kind of hybrid light and excitations to be conducted in a two-dimensional material we have created,” added Dr. Sriram Guddala, postdoctoral fellow in Professor Khanikaev’s group and the first author of the manuscript. “This method also allows us to change the direction of scattering of vibrations along these channels, forward or backward, simply by shifting polarizations in the incident of the incident laser beam. Interestingly, when phonon polytones multiply, the vibrations also rotate along with the electric This is a completely new way of controlling and rotating lattice vibrations, which also makes them helical. “
Entitled “Topological phonon-polariton funnel in mid-infrared metasurfaces”, the study appears in the journal Science.
Vibration encounters – phonon polaritons encounter molecules
S. Guddala et al., Topological phonon-polariton funnel in medium-infrared metasurfaces, Science (2021). DOI: 10.1126 / science.abj5488. www.science.org/doi/10.1126/science.abj5488
Provided by City College of New York
Citation: Researchers announce photon-phonon breakthrough (2021, October 8) retrieved October 8, 2021 from https://phys.org/news/2021-10-photon-phonon-breakthrough.html
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