Researchers announce photon-phonon breakthrough

New research by a team from City College of New York has discovered a new way to combine two different states of matter. For one of the first times, topological photons – light – were combined with lattice vibrations, also known as phonons, to manipulate their propagation in a robust and controllable way.

The study used topological photonics, an emerging direction in photonics that takes advantage of fundamental ideas in the mathematical field of topology about conserved quantities – topological invariants – that remain constant when changing parts of a geometric object under continuous deformations. One of the simplest examples of such invariants is the number of holes, which, for example, makes the donut and the cup topologically equivalent. Topological properties give photons helicity, as photons rotate as they propagate, leading to unique and unexpected characteristics, such as robustness to defects and unidirectional propagation along interfaces between topologically materials. distinct. Through interactions with vibrations in crystals, these helical photons can then be used to channel infrared light as well as vibrations.

The implications of this work are broad, notably allowing researchers to advance Raman spectroscopy, which is used to determine the vibrational modes of molecules. Research is also promising for vibrational spectroscopy, also known as infrared spectroscopy, which measures the interaction of infrared radiation with matter by absorption, emission, or reflection. This can then be used to study, identify and characterize chemicals.

“We coupled helical photons with lattice vibrations in hexagonal boron nitride, creating a new hybrid material called phonon-polaritons,” said Alexander Khanikaev, senior author and physicist affiliated with the Grove School of Engineering at CCNY. “It’s half light and half vibrations. Since infrared light and network vibrations are associated with heat, we have created new channels for the propagation of light and heat together. As a rule, network vibrations are very difficult to control and guide them around faults and sharp angles. was impossible before. “

The new methodology can also implement directional radiative heat transfer, a form of energy transfer in which heat is dissipated by electromagnetic waves.

“We can create channels of arbitrary shape so that this form of hybrid excitations of light and matter is guided in a two-dimensional material that we have created,” added Dr Sriram Guddala, postdoctoral researcher in Prof. Khanikaev’s group and first author of the manuscript. “This method also allows us to change the direction of vibration propagation along these channels, forward or backward, simply by changing the direction of polarization of the incident laser beam. Interestingly, as the phonons -polaritons propagate, the vibrations also rotate with the electric current. This is an entirely new way of guiding and rotating the vibrations of the network, which also makes them helical. “

Entitled “Topological phonon-polariton funneling in midinfrared metasurfaces”, the study appears in the journal Science.