Temperature-dependent thermal conductivities of one-dimensional nonlinear Klein-Gordon lattices with soft on-site potential

摘要

The temperature-dependent thermal conductivities of one-dimensional nonlinearKlein-Gordon lattices with soft on-site potential (soft-KG) have beeninvestigated systematically. Similar to the previously studied hard-KGlattices, the existence of renormalized phonons has also been confirmed insoft-KG lattices. In particular, the temperature-dependence of renormalizedphonon frequency predicted by a classical field theory has been verified bydetailed numerical simulations. However, the thermal conductivities of soft-KGlattices exhibit opposite trend in the temperature dependence in comparisonwith the hard-KG lattices. The interesting thing is that both thetemperature-dependent thermal conductivities of soft- and hard-KG lattices canbe interpreted in the same framework of effective phonon theory. According tothe effective phonon theory, the exponents of the power-law dependence of thethermal conductivities as the function of temperature are only determined bythe exponents of the soft or hard on-site potentials. These theoreticalpredictions have been consistently verified very well by extensive numericalsimulations.