Hello friend, using the contrast in labels without supervised labels usually is referred to as a "contrastive predictive coding". Contrastive because you're using contrast between embeddings, predictive because...well you get it

For your consideration though the term "triplet loss" applies what you're describing...just in a supervised mode. And dual-encoder retrieval systems are used for semantic search

I'm on a bus rn and gotta run I hope these at least help you in your search :)