Mumbai: History was made recently when the scientists of Tata Institute of Fundamental Research created the Bose-Einstein Condensation (BEC) phenomenon, which was predicted 82 years back by two great scientists Albert Einstein and Satyendra Nath Bose.
Being the first and only BEC in India, the TIFR finding was a special among the four or five labs in the world which have achieved BEC in optical traps.
“The creation of this exotic state of matter was one step in our research program to understand the fundamental interactions in the physical world,” says the Principal scientist Prof C S Unnikrishnan of the ‘Fundamental Interactions Laboratory´ of TIFR.
The TIFR scientists used magnetic fields and lasers to cool atoms to an extremely low temperature just above minus 273.15 degrees Celsius, or absolute zero and created a Bose-Einstein Condensate.
The scientists cooled a gas of atoms of the element rubidium to such a low temperature that a cluster of tens of thousands of atoms behaves as a single “superatom”. And each atom overlaps every other atom to make a giant ‘matter wave´ which is the hallmark of BEC, said Unnikrishnan.
The tiny cloud of atoms can ‘flow without resistance´.
The phenomenon has close connection to familiar superconductivity, and super fluidity in liquid helium, he said.
A BEC has only a short existence barely a few seconds. The ultra-cold atoms need to be confined in special “traps” created by either magnetic fields or lasers and maintained in ultra-high vacuum. Any contact with air will destroy a BEC.
More details of the experiment and pictures can be found at the laboratory website www.tifr.res.in/filab.
While most BECs in the world are confined within magnetic fields, the TIFR team used lasers to create and trap the BEC in a high vacuum stainless steel-glass chamber. The first optimally-trapped BEC was produced by scientists at the Georgia Institute of Technology in the US in 2001.
Unnikrishnan said, this was considered a difficult route and we chose this as we were confident of making it work.
Physicists Eric Cornell, Carl Wieman, and Wolfgang Ketterle in the US beat the world to a BEC in 1995 for which they got the Nobel Prize in 2001. Since then, dozens of laboratories across the world have produced BECs.
“In India, TIFR is the first one to produce BEC and “it was also produced in a relatively short time of less than a year of experimentation and at every stage we had to take care to have the largest number of coldest atoms, a prerequisite for creating a sure-shot BEC,” he said.
Bose-Einstein condensate results from a phenomenon predicted by Einstein in 1924 for a gas of atoms or molecules based on the ideas presented by Indian scientist S N Bose in the same year in the context of the spectral distribution of light called the Planck spectrum of black body radiation.
Bose insisted on dealing with the problem by treating light as a collection of particles of light (photons), deviating from the earlier treatments, Unnikrishnan said.
He managed to arrive at the correct law, in effect assuming that photons are indistniguishable particles and that any number of them can occupy a given state of being without restriction.
“We were strongly motivated to have a BEC in the land where the idea originated and we didn’t want to delay this further, ” Unnikrishnan added.
A BEC is an excellent tool to test physics theories and to probe exotic physical phenomena,“ said Unnikrishnan adding “our work on BEC have been reported in several international meetings and will appear in a forthcoming issue of the ‘Journal of Physics: Atomic and Molecular Physics´.”
One of the main reasons for working on this phenomenon was that the behaviour of this ‘super atom´ is very sensitive to interactions from light and environment. “It fits well with our deep interest in fundamental interactions, especially gravity, on which our lab is working for many years, he said.
Our interest in this phenomenon, go to a much deeper level in physics since it is known that there are two kinds of fundamental particles in nature with very different behaviour when a pair of more particles get together, called the ‘statistics´.
The particles that have an integer unit of angular momentum can form BEC, and any number can occupy the same state. They are called Bosons, named after S N Bose, and there is another kind, called Fermions, after physicist E Fermi (who also pioneered controlled nuclear fission) and only one particle can occupy a specific state of being.
In fact most fundamental particles are like that, like electrons, protons, neutrons, and they are characterized by a half integer value of angular momentum or spin.
Of course a composite particle made of these Fermions can be either a Boson or a Fermion based on the number of particles contained within. So, atoms made of Fermionic electrons and nucleons can be finally a Boson, and then make BEC.