The effect of nonlinearity on the efficiency of a thermal rectifier in the form of a junction of two chains

A thermal diode or rectifier is a heat conductor whose thermal conductivity depends on the sign of the temperature gradient. The junction of two beta-Fermi-Pasta-Ulam-Tsingou (β-FPUT) chains with anharmonic on-site potentials is considered here as a thermal rectifier. First, the linear case is analyzed and it is shown that in thermal equilibrium, when the energy is uniformly distributed among all phonon modes, the energy flux through the junction does not depend on its direction, in other words, the junction of harmonic chains does not act as a thermal diode. The thermal diode effect is observed in the harmonic system when the energy is unevenly distributed among the phonons. It is also observed when anharmonicity is taken into account. The results of this work are useful in analyzing the thermal conductivity of nanomaterials. © 2025 Elsevier B.V., All rights reserved.