A rule of physics that stood for a hundred years turns out to be 'broken' when it comes to materials like graphene.
March 24, 2026
Original Paper
Multiscale Violation of Onsager Reciprocity: Thermomechanical Proof, Atomic Evidence, and Graphene Predictions
arXiv · 2603.20773
The Takeaway
Onsager reciprocity is a bedrock principle stating that certain physical processes must be symmetric. However, researchers showed that 'entropy-weighted' effects at the atomic scale can create a fundamental asymmetry, potentially forcing a rewrite of how we understand heat and energy transport.
From the abstract
Onsager reciprocity $L_{ij}=L_{ji}$ is a cornerstone of near-equilibrium thermodynamics derived from microscopic time-reversal symmetry. We develop a geometric framework in which entropy-weighted reparameterization of thermodynamic response functions leads to an effective asymmetry in cross-couplings without violating the microscopic Onsager theorem. Motivated by the parallel structure of heat capacities $C_p$ and $C_v$, we introduce entropy-weighted response variables $\lambda_p$, $\lambda_v$,