Scientists create a new state of matter, the supercrystal, using lasers.
The study reveals that, at room temperature, the super crystal is stable.
A superb crystal was created by researchers at Pennsylvania State University and the Argonne National Laboratory, representing a new state of matter that is stable over a long period.
The purpose of the research team is to discover states of matter with unusual properties that do not exist in equilibrium in nature.
“We are looking for hidden states of matter, removing matter from its comfortable state, which we call the ground state,” says Venkatraman Gopalan, a professor of materials science at Pennsylvania State University.
“We do this by exciting the electrons in a higher state using a photon, and then observing while the material returns to its normal state.
The idea is that in the excited state, or a state that it passes in the blink of an eye on the path for the ground state, we will find properties we would like to have as new forms of polar, magnetic, and electronic states.”
But finding such states is not an easy task, of course, since it is a great challenge to maintain the intermediate state of matter, which can only exist for a small fraction of a second and then disappear.
However, the researchers found that at room temperature, the supercrystal is stable.
According to Gopalan, this process is like a snowball rolling down the side of the mountain that will not stop until it reaches the bottom unless something gets in the way.
The team did this by “frustrating the system” – not allowing the material to do what it wanted to do, which is to minimize its energy.
To perform the experiment, the researchers used unique atomic layers of two materials, lead titanate and strontium titanate, stacked in layers alternating one over the other to form a three-dimensional structure.
Lead titanate is a ferroelectric, a polar material that has electrical polarization, generating positive and negative electrical poles in the material.
Strontium titanate is not ferroelectric material, however. This incompatibility forced the vectors of electrical polarization to take an unnatural path, bending over themselves to make vortices.
These layers were grown between the two materials, on top of a substrate whose crystals were of an intermediate size, creating another barrier.
As a result, the strontium titanate layer tried to stretch to fit the crystal structure of the substrate, and the lead titanate had to compress to conform to it.
This put the whole system in a delicate but “frustrated” state, with multiple phases randomly distributed in volume.
The researchers reached the material with a laser that pours free charges into the material, adding extra electrical energy to the system, taking it to a new state of matter, a supercrystal.
These structures have a unit cell – the simplest repeating unit in a crystal – much more significant than any ordinary inorganic crystal, with a volume one million times larger than the unit cells of the two original materials.
The material finds this state on its own.
Unlike transient states, this super crystalline state remains at room temperature. It is compromised when heated to about 350 degrees Fahrenheit (approximately 149 degrees Celsius).