In a new study, researchers from AMOLF, together with their international colleagues from Germany, Switzerland, and Austria, have developed a unique type of material that changes the way sound waves move and are amplified.
This new material, known as a metamaterial because it’s engineered to have properties not found in nature, could lead to significant advancements in sensor technology and the way we process information.
At the heart of their discovery is what’s called a “bosonic Kitaev chain.” This might sound complicated, but it’s essentially a chain of tiny, vibrating parts called resonators, which can amplify sound waves in a way never seen before.
This chain is special because it deals with bosons (the particles that carry forces like light and sound) instead of electrons, which behave very differently.
The idea came from a theory about electrons in a special kind of material that could superconduct electricity without resistance.
The theory predicted something amazing: certain particles could exist at the ends of a wire made of this material, which could be incredibly useful for building quantum computers.
The researchers were fascinated by this and wondered if a similar concept could apply to bosons and sound waves.
To create this metamaterial, the team used tiny silicon strings on a chip, making them vibrate using the pressure from laser light. By adjusting the laser’s intensity over time, they connected five of these resonators together in a way that mimics the theoretical chain.
The results were astonishing. Unlike in traditional materials, where sound can move back and forth freely, in this bosonic Kitaev chain, sound waves are massively amplified as they move along the chain in one direction.
If the sound tries to go the opposite way, it’s blocked entirely. Even more intriguing, by slightly delaying the sound wave, this direction can be reversed, creating a kind of directional amplifier for sound that could have many practical applications, especially in quantum technology.
This metamaterial is also a topological material, which means its properties are very stable and resistant to imperfections.
This stability comes from the material’s mathematical characteristics, ensuring that its special behavior remains intact even if it’s not perfectly made or gets damaged.
This concept of topological materials has been a hot topic in physics, earning a Nobel prize in 2016. However, those materials didn’t include the possibility of amplification, making this new discovery even more exciting.
The team also demonstrated that if they form the chain into a loop, like a necklace, the amplified sound waves keep going around in circles, reaching very high intensities. This is somewhat similar to how lasers work with light, but now with sound.
One of the most promising aspects of this research is the potential for new sensor technologies. The material’s unique properties mean it could be incredibly sensitive to tiny changes, such as the addition of a small molecule or the presence of a quantum bit (qubit).
This sensitivity, combined with the material’s stability, could make for highly accurate sensors that are less affected by noise or other disturbances.
The researchers are just beginning to explore the full potential of this discovery. They believe it could lead to better, more sensitive sensors and have many other applications yet to be imagined.
This breakthrough is not just a step forward in understanding the physics of sound and materials but could also have practical impacts on technology and information processing in the future.
The research findings can be found in Nature.
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