Pioneering research by IITKgp Faculty has opened up opportunities for the development of quantum devices. Prof. Sajal Dhara who joined the Department of Physics at IIT Kharagpur in 2016, has found harmful mass particles of polaritons which are composed of half-light and half-matter. Prof. Dhara and his contributors at the University of Rochester and ICTS, Bangalore have found new insights on the mass of such absorbing particles. The modern understanding is supposed to inspire a giant leap towards futuristic technology development.
The investigation has been highlighted in the honoured ‘Nature Physics’ journal in their October 2017 issue. The contributors included in this work are Dr C. Chakraborty, Dr K. M. Goodfellow, Dr L. Qiu, Dr T. A. O’Loughlin, Prof. G. W. Wicks, and Prof. A. N. Vamivakas, all from the University of Rochester and Prof. Subhro Bhattacharjee from ICTS, TIFR.
Light is an electromagnetic wave, though it also displays particle properties with zero mass. Matters on the other hand made of atoms with a certain mass. Investigators can artificially create a combined particle state that is made of half-light and half-matter, known as polaritons.
Prof. Dhara Stated that “You can imagine a caricature version of polaritons just like tiny fireflies being laws of physics which is distinct from our classical world.”
We all know that light gets bounced by a mirror. Let’s imagine what will happen between two mirrors: light will reflect back and forth and gets trapped in the space between mirrors, thus forming an optical cavity. Whenever any light is an emitting gas of atoms, in this case, it is called excitons is placed inside the optical cavity, particles of light get absorbed and re-emitted several times before it finally leaks out from the hole. In this process, the exciton and the photon lose their individuality and forms a composite state altogether known as exciton-polaritons. Mass of such polaritons thus formed is lighter than the mass of an electron by a factor of 0.00001.
This unique ultra-low mass characteristics of these particles are what would lead to the possible devices of future dissipation-less polaritonic devices close to room temperature or as a householder would put as ‘ushering an era which will witness a giant leap from smart electronic to smarter polaritonic devices, realizing the dream – the future is here.’ This research will also lead to the improvement of a new generation of optoelectronic devices.
Exciton-polaritons are Bosons which obey the well-known Bose-Einstein statistics found by S. N. Bose and A. Einstein who also foretells a new condensation state of such particles known as Bose-Einstein condensation.
Prof. Dhara who is the leading author of the paper continued “So far BEC has been accomplished at ultra-cold temperatures close to -273 degree Celsius. One of the main concerns in this field is due to the possibility of realization of Bose-Einstein Condensation of gas made of exciton-polaritons closer to room temperature. This will open up probabilities for the development of quantum devices. We can now imagine dissipation less polaritonic devices in future that can work at room temperature.”
The new conclusions that the work presented by Prof. Dhara and coworkers shows that the particles not only have ultra-low mass but it can also become harmful if the particles become charged up with additional electrons.
Prof. Dhara has received substantial funding from MHRD, ISIRD and the SERB Ramanujan Fellowship research grant for expanding his lab facilities at IIT Kharagpur. One of the long-term goals of the ‘Nanoscale Optoelectronics’ lab would be to study the light-matter interaction for the advancement of futuristic technologies and basic science.