By: Natalie Oulikhanian
Our world is made up of atoms; however, the way that these atoms exist within matter can vary drastically. Defining different states of matter will depend on their qualitative properties such as its assigned mass and ability to fix its shape in a container. We see these differences in our everyday life, which is limited to only four observable states of matter around us — solids, liquids, gases, and plasma. These four states have continuously been a central focus for research in physics throughout history. It was only until the 1990s that a fifth state of matter, with its own unique set of properties, was created in laboratories and given the name “Bose-Einstein condensates” after its key quantum theorists Albert Einstein and Satyendra Nath Bose.
A Bose-Einstein condensate is a group of gas atoms cooled only a few hundred billionths of a degree from absolute zero, the lowest theoretical temperature possible. To understand why temperature plays such a significant role in the definition of unusual matter such as Bose-Einstein condensates, we must explore how particles react to a change of temperature or energy. Put simply, as the temperature rises, atoms within matter will move and vibrate more actively while being more spaced out from their surrounding atoms. Conversely, a decrease in temperature will cause the particles to vibrate less and move closer to each other. We cannot cool matter infinitely, however. From how much current research explains, nothing in our universe — including what is done in labs — has ever reached or probably ever will reach the theoretical limit to “coldness.” However, this does not restrict states of matter like Bose-Einstein condensates from forming as the only property they require is a temperature very close to the absolute zero.
When atoms become incredibly close to each other through a shift in cooler temperatures, their spacing is not the only quality that is affected. In reaching temperatures shy a hair from absolute zero, atoms will begin to be indistinguishable from one another. If one were to look at two particles at this temperature, they would not be able to find any discernible traits by observing their wave-function — or the function that contains and represents information about a physical particle’s unique position and momentum. This removal of individuality is derived from the inherent ability for atoms and other quantum-scale objects to exist and behave not only as particles but also as waves. As temperatures decrease, their wave-like properties become more evident. The particles in this position are named “bosons” after the same scientist, Satyendra Nath Bose, credited for the discovery of our Bose-Einstein condensates. A popular example of a common boson is the photon, or a particle of light which is notably used to explain the concept of particle-wave duality in quantum mechanics. When these waves interfere and interact with other unidentifiable atoms within the matter, they begin to act as one single super-atom and collapse into the lowest energy level. When one tries to measure where the atoms are, one sees more of a fuzzy ball shape instead of discrete locations.
To make the transition from many free-roaming atoms into a super-atom clearer, it is possible to look at the waves in nature, such as those in a body of water. For example, if someone were to be skipping rocks and multiple ripples form, these ripples will continue being created into larger waves. If two or more of these ripples were to collide with one another, a new shape of a wave will be formed that conforms to how the original waves looked like. This newly generated wave can be perceived as the “super-atom” of which Bose-Einstein condensates are.
The potential uses and applications for Bose-Einstein condensates are still in its basic research. The novel state of matter still has enough unknowns before researchers implement its profound qualities and behaviour. For example, condensates are not found naturally on Earth without the use of laboratories, making it difficult to fully understand the properties of this matter. Bose-Einstein condensates are notably related to two remarkable low-temperature phenomena, superfluidity and superconductivity. Superfluids form a liquid that flows with zero friction whereas electrons in a superconductor move through a material with zero electrical resistance. However, what might be most intriguing from the variety of unique properties Bose-Einstein condensates have is its ability to slow down light. This quality has found profound potential in telecommunications, storage of data, and quantum computing.
The low-temperature requirements of Bose-Einstein condensates propose practical difficulties and issues in efficiency. There are further bells and whistles such as lasers and magnets that take patience to calibrate before Bose-Einstein condensates become commercialised. However, curiosity dominates all research. With the interest that Bose-Einstein condensates are creating about other concepts in physics and quantum mechanics, the state of matter will deepen our knowledge on the state of the never-ending bizarre behaviour in the world around us.
Comprehension Questions:
How are Bose-Einstein condensates different from other states of matter?
In the observable states of matter, the atoms present are experienced as separate distinguishable particles, however the atoms in Bose-Einstein condensates will no longer have their identifiable properties defined in a wave-length function. Rather, the atoms begin to form and behave as an almost “super-atom” state where atoms will collapse to the same energy level.
What must be done to form a Bose-Einstein condensate?
Bose-Einstein condensates, like other low-temperature phenomena, can only be formed in temperatures close to the absolute zero, or the lowest theoretical temperature possible. It is only at this temperature when the atoms’ identifiable features are lost.
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