Well, congrats that your interview is over!

The research paper was just an example, since you asked about extra stuff to bring (kind of - hey, if you have it, cool! bring it along)! LOL! People have all sorts of things, such as publications, extra LOR, research paper (as mentioned before ) , and the list can go on and on... So, for the students who are still awaiting their interview, you DO NOT have to bring anything extra to the interview, but if you have something you want to share - cool, bring it along...

Good luck to you all!