It's definitely not common these days to send a thank you note. It used to be a lot more common 20+ years ago but these days, it's pretty uncommon from my experience.

But I don't think there's anything wrong with sending a very brief, succinct thank you email to your interviewer(s). And in one case, someone I know got a job at Cisco because she sent a well-written thank you letter to the interviewer, because it put her in their minds before they decided among 10 similarly-qualified candidates. Keep it short and on point, with maybe one sentence about something they mentioned when talking with you. There is definitely an art to writing a 2-4 sentence, non-awkward email.

Personally I think a hand-written note would be weird, I wouldn't do it.