Quasi-Casimir coupling can induce thermal resonance of adsorbed liquid layers in a nanogap

Abstract

In a vacuum nanogap, phonon heat transfer can be induced by quasi-Casimir coupling in the absence of electromagnetic fields. However, it is unknown whether phonons can be transmitted across a nanogap via solid-like liquid layers adsorbed on solid surfaces. Here, we elucidate that phonon transmission across a nanogap can be induced by quasi-Casimir coupling via adsorbed liquid layers using classical nonequilibrium molecular dynamics simulation. We modulated the gap distance to verify the existence of quasi-Casimir coupling between interfacial solid–liquid or liquid–liquid layers. Thermal resonance can be induced between two liquid layers by quasi-Casimir coupling, agitating the co-occurrence of thermal resonance between interfacial solid layers, while a liquid monolayer disturbs the resonance. The thermal resonance between liquid layers results in a larger heat flux and thermal gap conductance compared with those in the vacuum gap case, while the liquid layer limits the acoustic phonon transmission in the interfacial solid layers. The fundamental understanding of quasi-Casimir heat transfer at the solid–liquid interface could pave the way for future nanoscale energy transport and thermal management.