Novel about people inserting disks in their brains

I was reading a novel but didn't finish it and now I can't remember what it's called.

Humanity has established contact with what appears to be a much more advancei civilization. The aliens establish a small trade mission on Earth and hire humans to work for them. They implant a device in some of the human's heads which allows you to load a disk containing knowledge / skills - you put the disk in and become a neurosurgeon but then at the end of the work day, you have to return the disk and you lose the skills.

The aliens are friendly and polite, but look down on humans, dismiss human science as waste of time, etc. There is very little research done on Earth, everyone just turns to the aliens for a disk containing whatever skills, tech, knowledge they need.

There is long discussion on string theory etc in the narrative.

At some point something goes wrong with the aliens' home planet (I think) and their science can't explain it, so in desperation they have to turn to human theories that they've dismissed as work of primitives.

Does anyone know what's the name of this novel?