New research by a team from the City College of New York has discovered a novel way of combining two different states of matter. For the first time, 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, an emergent direction in photonics that takes advantage of fundamental ideas from the mathematical field of topology about conserved quantities - topological invariants - that remain constant when altering 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 endow photons with helicity, as the photons rotate as they propagate, resulting in unique and unexpected characteristics such as robustness to defects and unidirectional propagation along interfaces between topologically dissimilar materials. Thanks to the interactions with the vibrations of the crystals,
The implications of this work are broad, and in particular allow 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 through absorption, emission, or reflection. This can be used to study, identify, and characterize chemicals.
"We couple the helical photons with the vibrations of the hexagonal boron nitride lattice, creating a new hybrid matter called phonon-polaritons, " explains Alexander Khanikaev, lead author and physicist affiliated with the Grove School of Engineering at CCNY. " It is half light and half vibrations. As infrared light and web vibrations are associated with heat, we have created new channels for the propagation of light and heat together. Normally, web vibrations are very difficult to control. , and guiding them around flaws and sharp corners was impossible before."
The new methodology can also implement directional radiative heat transfer, a form of energy transfer during which heat is dissipated through electromagnetic waves.
"We can arbitrarily create channels for this form of hybrid light and matter excitation to be guided along a two-dimensional material that we have created, " added Dr. Sriram Guddala, a postdoctoral researcher in Professor Khanikaev's group and first author. of the manuscript. "This method also allows us to change the direction of propagation of the vibrations along these channels, forward or backward, simply by changing the polarization of the incident laser beam. Interestingly, as the phonon-polaritons propagate, the vibrations also rotate along with the electric field. It is a totally new way of guiding and rotating the vibrations of the net, which also makes them helical."
Source: Science