We all know about matter and its three states and about plasma, the hot ionized gas considered as the fourth state, but we have seldom heard of something called as the fifth state of matter. In 1924, Albert Einstein and Satyendra Nath Bose predicted the “Bose-Einstein condensate” (BEC), which is  referred as the fifth state of matter.

What is Bose-Einstein condensate (BEC)?

A Bose-Einstein condensate (BEC) is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zero (that is, very near 0 K or ?273.14 °C). Under such conditions, a large fraction of bosons occupy the lowest quantum state, at which point macroscopic quantum phenomena become apparent.

How Bose-Einstein condensate (BEC) developed?

Bose first sent a paper to Einstein on the quantum statistics of light quanta (now called photons). Einstein was impressed, translated the paper himself from English to German and submitted it for Bose to the Zeitschrift für Physik, which published it.

The Einstein manuscript,which was once assumed to be lost, was found in a library at Leiden University in 2005. Einstein then comprehended Bose’s ideas of matter in two other papers that resulted in a concept of Bose gas, which is governed by Bose-Einstein statistics, and describes the arithmetical distribution of the same particles with figure spin, now called bosons.

Bosons, actually  include the photon as well as atoms such as helium-4 (4He), which are allowed to share a quantum state. Einstein proposed that cooling bosonic atoms to a very low temperature would cause them to fall (or “condense”) into the lowest accessible quantum state, resulting in a new form of matter.

It was Einstein who guessed that these same rules might apply to atoms. He worked out the theory for how atoms would behave in a gas if these new rules applied. What he found was that the equations said that generally there would not be much difference, except at very low temperatures. If the atoms were cold enough, something very strange was supposed to happen. It was so outlandish he was not sure it was correct