Some people here are getting hung up on what exactly "sentience" is, but I'm just going to leave that argument at the door and give you the solid dick.
The word you're looking for is literally just "slave".
Like, even the word "robot" itself is from the Czech for "serfdom" or "corvée", so ever since exactly such a machine as that you describe was first imagined by science fiction writers, it has been likened to indentured servitude and to unpaid forced labor. So that is the role that this "sentient AI" would play: a slave in the most traditional sense is what someone is when thon can understand and try to act on sy conditions and interests, while being wholly owned by an entity that compels thon to work for said entity without pay and without rights.
I think that being a good materialist means understanding exactly when a detail of something actually makes a difference in practice: metal or flesh, a sapient robot has a lot more in common with a human chattel slave than with a decidedly non-sapient machine. This is not to say that the lives of such robots would not differ in any way from the lives of human slaves, because obviously there would be plenty of differences, but these differences are still a separate discussion from the actual relationship to production.
Anyways read Yokohama Kaidashi Kikou