How do I approach a professor for research
I've advised nearly 30 Ph.D. students during my academic career as a professor. My advice to you is to be careful here. You've sent him a few emails, and you've received no response. Hopefully you attached your CV to those emails. If he is looking for someone to join his research group and he thought you were an exciting candidate, he should have responded to one of your emails by now (or maybe he still will). Given that you are already in the program, he really should either invite you to meet with him or else let you know that he doesn't have an opportunity for you. Given his lack of responsiveness, maybe he isn't a very good choice as a research advisor in any event.