As you are a research oriented student then the thing that you should focus on is your interest.

The subjects you have mentioned have their respective field as well as interdisciplinary field. For example Indian have been trying to start development of Quantum Computing. Now in this scenario you can see that the project need Physicist , Computer scientist , Mathematicians , Scientist specialized in (Solid state physics [which can be pursued by Physicist , Chemist , Engineers ]) etc to do so.

India is developing its research facilities with time to time and thus you will have a good scope for research in any subject but the scope can't justify your interest. So you should find out your area of interest and pursue. While pursuing you go through a number of subjects and teachers and thus you will keep growing interest in the field and that will give you a proper vision about your proper expertise you want to pursue.

I hope my answer will give you a scenario. Wish you a great career ahead.