If the paper's claim is correct, it would literally be the creation of Maxwell's Daemon.
I am banking on the author not fully understanding their own experiment, rather than a complete overturning of thermodynamics. I would be very excited to be wrong, though.
Not if it produces less heat than it converts, the rest being lost as ... ah, wait a minute. Well anyway it would only produce as much heat as it converts, so this perpetual cycle couldn't do any useful work. Perpetual useless motion is allowed, isn't it?
Oh, I see it now, you're suggesting that it could just passively create a gradient that could produce power in a more conventional way, like via an engine, until I guess the device kicks in again and re-establishes the gradient (producing more power of its own in the process). Yes. That does sound like impossible free energy.
I suppose if we’re assuming that overturning thermodynamics is the byline, such a machine could exist without being a perpetual motion machine if somehow the energy that produces the machine’s work was lost as say… nuclear radiation instead of heat?
Or perhaps requiring some kind of catalyst that is rendered into a higher energy state which is functionally useless for its purpose as said catalyst?
Either way, we’ve got some interesting sci-fi concepts to work with!
I wouldn't hold your breath on being wrong. A device that converts heat into electricity without a gradient is a perpetual motion machine. Consider what would happen if you popped such a device on one side of a thermoelectric plate, and used its output to power a heater on the other side of the plate. The arrangement would permanently maintain a gradient across the thermoelectric plate - free electricity forever!