Unveiling the Peculiar World of Supersolids
Think of a flawless diamond whose internal components move without any resistance, or an ice cube whose closely-arranged components slide smoothly. These scenarios might seem odd or even unachievable, but for physicists, they are quite similar to a peculiar state of matter they recently developed, called a supersolid.
Over the past few years, scientists have been producing supersolids on a minuscule scale in laboratories. Recently, a team of physicists developed the most advanced supersolid to date: a two-dimensional supersolid, resembling a sheet of paper. They published their findings in Nature last Wednesday.
Matthew Norcia, a physicist at Innsbruck University in Austria and the lead author of the Nature paper, states that it has always been a significant objective to develop supersolids in two dimensions.
So, what is a supersolid? Fundamentally, it possesses attributes of two distinct states of matter — one ordinary and the other rather mysterious.
The Intriguing Blend of Solid and Superfluid
The second state of matter, which might be less familiar to you, is a superfluid. As a result of quantum mechanics, a superfluid behaves like a fluid with no viscosity. Scientists have observed superfluids by cooling helium to temperatures just above absolute zero. These superfluids can easily climb walls or glide over surfaces.
A supersolid fuses both a solid and a superfluid into a single entity: a solid that flows like a fluid without friction or resistance. While this may sound peculiar, it is entirely natural and a consequence of quantum mechanics, the unique branch of physics that governs the universe at the smallest scales.
Bruno Labruthe-Tolra, a physicist at Sorbonne Paris North University in France who was not involved in the recent paper, provides an analogy for understanding supersolids in Nature News & Views accompanying the new study: “Imagine an ice cube submerged in liquid water, where the water flows through the cube without any friction.”
The Evolution of Supersolid Research
The concept of a supersolid isn’t entirely new; physicists have been proposing it since the 1960s. However, for many years, it was unclear if we could create a supersolid on Earth. It wasn’t until the 2010s that scientists started making tangible progress in developing supersolids in laboratories.
Initially, scientists attempted to find supersolids in supercooled helium. Since superfluids occur in helium due to its atomic properties, it seemed reasonable to search for supersolids within it as well. However, this approach has not yet been successful.
Later in the decade, physicists shifted their focus to other elements, such as rubidium and lanthanum. When a small number of gaseous atoms are trapped and cooled to just a fraction of a degree above absolute zero (approximately -460 degrees Fahrenheit), they transform into an array of quantum oddities known as a Bose-Einstein condensate.
To produce a supersolid, atoms are first trapped, then cooled, and finally, their interactions are manipulated. “By tuning these factors correctly, and adjusting the shape of the trap, you can achieve a supersolid,” explains Norcia, the lead author.
In 2019, researchers employed this technique to create a basic, one-dimensional supersolid, which essentially resembles a thin, straight-line tube of supersolid material.
Progressing from One-Dimensional to Two-Dimensional Supersolids
Norcia and his colleagues at Innsbruck University and the Austrian Academy of Sciences have accomplished this progression. By adjusting the apparatus used to trap atoms and the method for condensing them, they managed to expand their supersolid from one dimension into two, transforming it from a minuscule tube into a thin sheet.
Labruthe-Tolra explains that this breakthrough is significant because studying a system’s properties under rotation is a direct way to prove superfluidity, which cannot be achieved if the system is only one-dimensional.
With the successful creation of a two-dimensional supersolid, the question arises whether researchers can develop a three-dimensional supersolid that could be touched. Norcia indicates that it’s unlikely to happen soon, though the idea has intrigued physicists. He is unsure how this could be accomplished with the current technology.
Instead of pursuing a three-dimensional supersolid, the researchers plan to study the two-dimensional supersolid they’ve produced. Despite successfully creating a supersolid, there is still much to learn about its properties and behavior.
What Does All This Mean?
The development and study of supersolids, particularly two-dimensional supersolids, have significant implications for the scientific community and humanity as a whole. Understanding and exploring these unique states of matter can contribute to various areas:
- Advancing the understanding of quantum mechanics: Supersolids are a product of quantum mechanics, and studying them can provide valuable insights into the behavior of matter at extremely small scales, further expanding our knowledge of the quantum world.
- Revealing new properties and phenomena: As researchers continue to investigate supersolids, they may uncover previously unknown properties or phenomena related to these materials. These discoveries could offer novel perspectives on the behavior of matter and potentially inspire new areas of research.
- Potential applications in technology: Although the practical applications of supersolids are still speculative, their unique properties, such as frictionless flow, could inspire the development of new technologies in areas like superconductivity, quantum computing, or materials science.
- Enhancing interdisciplinary research: The study of supersolids often requires collaboration between physicists, chemists, and materials scientists. This interdisciplinary approach can lead to innovative ideas and foster cooperation between various fields of science.
- Inspiring the next generation of scientists: The investigation of supersolids and the breakthroughs made in this area can serve as an inspiration for young scientists, motivating them to pursue careers in research and contribute to the future advancement of science.
While the direct practical implications of two-dimensional supersolids may not be immediately evident, their study contributes to the broader understanding of quantum mechanics and the behavior of matter at small scales. This knowledge has the potential to unlock new scientific and technological advancements in the future.
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Original Article: https://www.nature.com/articles/d41586-021-02191-5