That's an example of a similar system, but probably impractical for use in an electronics context. I have in my imagination a fantasy "smart" material that in t

That's an example of a similar system, but probably impractical for use in an electronics context. I have in my imagination a fantasy "smart" material that in the limit can transfer 0.5 * k^m joules of heat per square meter per second from one side to the other (where m is somewhere between 1 and 2). Such a material would always feel slightly warmer on one side and cooler on the other, and this effect would actually increase in the presence of ambient heat, hence it could act as a thermal "brake" or active heat pipe/diode. I beleieve such a device is "allowable" within the laws of physics.