Approaching the perfect diode limit through a nonlinear interface

TL;DR

This study explores how nonlinear interfacial potentials influence thermal rectification in coupled particle chains, revealing that maximal rectification occurs near the infinite-square-well potential at low temperatures.

Contribution

It demonstrates that the optimal interfacial potential for thermal rectification approaches the infinite-square-well limit, regardless of the on-site potential type, and identifies the dependence on temperature and chain details.

Findings

Rectification is maximized near the infinite-square-well potential.

Optimal rectification depends on bath temperatures and chain parameters.

Maximal rectification occurs at low average temperatures.

Abstract

We consider a system formed by two different segments of particles, coupled to thermal baths, one at each end, modeled by Langevin thermostats. The particles in each segment interact harmonically and are subject to an on-site potential, for which, three different types are considered, namely, harmonic, $\phi^4$, and Frenkel-Kontorova. The two segments are nonlinearly coupled, between interfacial particles, by means of a power-law potential, with exponent $\mu$, which we vary, scanning from subharmonic to superharmonic potentials, up to the infinite-square-well limit ($\mu\to\infty$). Thermal rectification is investigated by integrating the equations of motion and computing the heat fluxes. As a measure of rectification, we use the difference of the currents resulting from baths inversion, divided by their average. We find that rectification can be optimized by a given value of $\mu$ that depends on the bath temperatures and details of the chains. But, regardless of the type of on-site potential considered, the interfacial potential that produces maximal rectification approaches the infinite-square-well ($\mu\to\infty$), when reducing the average temperature of the baths. Our analysis of thermal rectification focuses on this regime, for which we complement numerical results with heuristic considerations.