Supersolids, The Newest Super Cool Phase of Matter

As you might remember from grade school, there are four phases or states of matter that are observable to the average person: Solid, liquid, gas and plasma (lightning for example). But what you might not have learned in 5th grade science class is that between these four states are intermediate states, like liquid crystal, and outside these four states are “exotic” states of matter. “Exotic” states of matter can both occur “naturally”, such as within the atomic mystery vacuum of space, and within the lab. Such is the case with Supersolids.

It would seem obvious, and typically the Laws of Physics would agree, that a state of matter having the properties of both a liquid and a solid would be impossible. But that’s not how physicists roll. Supersolids have been theorized for decades but have only been observed on a 1D level, or nano, or the “tiniest of the tiny” level, in 2019.

And now they are no longer in the realm of the merely theoretical. Physicists were able to chill clouds of strongly magnetic atoms close to just above zero Kelvin (-459.67 degrees Fahrenheit) causing the particles to lean back and chill… or slow down by firing a laser at gas particles, a technique called laser cooling.  Once the atoms were as cool as possible, the researchers pulled back on the laser beam, allowing for the most energetic (or “warmer”) particles to escape (evaporative cooling) leaving just the super-cooled atoms and the space between.

This new phase of matter has a repeating, rigid structure but the internal molecules can move past each other without internal friction or viscosity. Particles in this state are both locked into a rigid solid structure (like an apple), but also delocalized at the same time (like applesauce) which allows them to behave like a wave and flow freely without friction throughout the solid (imagine applesauce holding the shape of an apple).

This is what is known as a 2D Supersolid. It’s a new phase of matter with currently no practical applications. Because that’s the real question. Why? Why does this exist? Why did physicists spend 50 years trying to observe it? Why even theorize a Supersolid with all these classic states of matter littering the planet?

To answer that, some context with Supersolid’s cousin, Superfluid. Superfluids, another lab created “exotic” state of matter, are characterized as a fluid with zero viscosity. This means there is no friction between atoms, allowing it to flow without a loss of kinetic energy. Put simply, Superfluid can climb up the sides and out of its container by using atomic cracks and space like a ladder. This quality also allows a vortex spun in a Superfluid (like swirling water in a glass) to continue spinning almost indefinitely.

The theoretical applications of Superfluid are, obviously, space. Developing, for example, a Superliquid lubrication that can move in all directions regardless of container would be really, really useful out in zero gravity. 

And it’s those Superfluid properties that have researchers so pumped to observe what a vortex will do in the newly observed 2D Supersolid. A vortex cannot happen in a solid state of matter, but it can in a liquid or gas state. If the state of Supersolid can contain vortices, it completely changes how physics and, by proxy, the scientific community views states of matter as they relate to the human experience. Imagine an ice cube sitting in water with frictionless flow of water THROUGH the cube. The theoretical practical applications are mind-boggling.

But the real answer as to the “why” behind developing Supersolids? It’s just super cool.