Use some conversation killers like:
– After they say something (but not a joke) say, “Was that the punch line? Because I don’t get it.”
– After they start talking to you, interrupt and change the subject by asking them if they heard of thigmotropism or use another obscure long word.
– Don’t give eye contact.
– One word monotone answers.
– When you walk in, don’t say hello. If they say hello, then lightly wave to them without any eye contact.
I’m sure you can think of more or look some up online.
After a few of their awkward attempts, they should realize that it’s not worth conversing with you.