Graduate One way vibrational energy transfer

[vin300]

https://www.sciencedaily.com/releases/2019/04/190403135011.htm
Yale University folks have come up with a new technology which they say can make sound as well as heat flow in one direction only. This is done by using a "standard cavity - optomechanical interaction to produce robust nonreciprocal coupling between phononic resonators". The journal reference in given at the bottom of the news article.
If they can control heat flow by turning a knob, what happened to the laws of thermodynamics? I haven't read the full journal article.

 

[Dale]

The original paper is here:
https://arxiv.org/abs/1807.03484
Note that the arxiv preprint has not yet been updated to reference the Nature article, hopefully they will do that later.

In the article the authors mentioned repeatedly that the breaking of reciprocity requires using a laser. In the section on cooling they mentioned the power of the laser, but not the power of the thermal transfer from one cavity to the other nor the temperatures of the two cavities.

The power of the laser represents work. Therefore the cooling provided here is simply a completely novel type of a heat pump.

As long as: $$\frac{Q}{W}\le \frac{T_C}{T_H-T_C}$$ the device obeys the second law of thermodynamics.

The article does not provide enough information to confirm that it does obey the second law, but it also does not provide any hint of a suggestion that it violates it. This article certainly wouldn’t support any supposition of a violation. In the absence of clear evidence to the contrary it is safe to assume that this new class of heat pump will satisfy the second law of thermodynamics.