Non-Reciprocal Systems

Most of our knowledge on heat machines, molecular machines and chemical networks is based on the assumption that at thermal equilibrium systems keep what is called local detailed balance. Local detailed balance means that, at thermal equilibrium, the rate between any pair transitions is perfectly balanced by the rate of the opposite transition.

Any deviation from this balance requires the system to be out of equilibrium, resulting in the flow of currents in mesoscopic junctions, the transformation of energy in solar cells, or the realization of several biological functions in living systems.

Breaking detailed balance is thus an essential thermodynamic resource with several applications.

Non-reciprocal systems have the peculiarity of breaking detailed balance even at equilibrium.

This has resulted in many surprising effects: persistent heat currents in thermal equilibrium, violations of the Kirchhff law, photon thermal hall effect and giant magnetoresistance for the heat flux.

We recently found that non-reciprocal materials are needed in order to build a heat engine based on Casimir forces. What other exciting effects can be produced by non-reciprocal systems?

We are investigating this question by building a thermodynamic framework to study non-reciprocal systems and discover other peculiar thermodynamic effects. Moreover, by examining the systems that do not comply with the common assumption of local detailed balance, we are exploring uncharted territories and sharpening the theory of thermodynamics.

These are

Some of the questions we are exploring:

Could non-reciprocity offer any advantages to heat machines or other devices?

What are the limitations that thermodynamics impose on these systems?

What is the basic thermodynamic behavior of non-reciprocal systems?


Some of our papers:

Casimir Heat Engine Using Non-Reciprocal Materials:

Gelbwaser-Klimovsky, D., Graham, N., Kardar, M & Kruger, M., Near field propulsion forces from non-reciprocal media. Physical Review Letters 126 (2021): 170401


Other Group's Papers:

Persistent Heat Currents In Thermal Equilibrium:

Zhu, L, & Fan, S., Persistent directional current at equilibrium in nonreciprocal many-body near field electromagnetic heat transfer. Physical review letters 117 (2016): 134303


Two Excellent Reviews On Non-Reciprocity

Electromagnetic Non-Reciprocity

Caloz, C., Alu, A., Tretyakov, S., Sounas, D., Achouri, K., & Deck-Léger, Z. L., Electromagnetic nonreciprocity, Physical Review Applied, 10 (2018): 047001​

Tutorial on electromagnetic Non-Reciprocity & Its Origins

Asadchy, V. S., Mirmoosa, M. S., Díaz-Rubio, A., Fan, S., & Tretyakov, S. A., Tutorial on electromagnetic nonreciprocity and its origins. Proceedings of the IEEE 108 (2020): 1684