Effect of coupling displacement on thermal current of Frenkel-Kontorova lattices

Effect of coupling displacement on thermal current of Frenkel-Kontorova (FK) lattices in the underdamped case is investigated by means of numerical calculations. The results indicate that: (i) as the system has less atoms and is symmetric, the coupling displacement can boost up its thermal current, and absolute value of the thermal current as a function of the coupling displacement exhibits one or two peaks, determined by period of the FK lattices. (ii) As the system with less atoms is asymmetric, the coupling displacement affects its thermal current only in the case of either negative temperature difference or positive temperature difference, depending on asymmetry of the on-site potentials of the FK lattices. The coupling displacement cannot only enhance negative differential thermal resistance effect but also regulate thermal rectifier of the system as a thermal switch. (iii) Along with an increasing atomic number of the FK lattices, the effect of the coupling displacement on the system gradually disappears. Our results have the implication that the coupling displacement between nonlinear lattices plays a crucial role in the design of thermal devices.