Anomalous (non-Fourier's) heat transport is no longer just a theoretical issue since it has been observed experimentally in a number of low-dimensional nanomaterials, such as SiGe nanowires, carbon nanotubes, and others. To understand these anomalous behaviors, exploring the microscopic origin of normal (Fourier's) heat transport is a fascinating theoretical topic. However, this issue has not yet been fully understood even for one-dimensional (1D) model chains, in spite of a great amount of thorough studies done to date. From those studies it has been widely accepted that the conservation of momentum is a key ingredient to induce anomalous heat transport, while momentum-nonconserving systems usually support normal heat transport where Fourier's law is valid. But if the nonconservation of momentum is the reason, what is the underlying microscopic mechanism for the observed normal heat transport? Here we carefully revisit a typical 1D momentum-nonconserving $ϕ^{4}$ model and present evidence that the mobile discrete breathers or, in other words, the moving intrinsic localized modes with frequency components above the linear phonon band can be responsible for that.
Novel ballistic to diffusive crossover in the dynamics of a one dimensional Ising model with variable range of interaction
自旋的动力学是由其相邻畴的大小决定的，这一观点是最近提出的（S。Biswas和P. Sen，Phys. Rev. E { \bf 80}，027101（2009））在伊辛自旋模型（此后，称为模型I）中进行。现在定义参数$p$以修改动力学，使得自旋可以在尺寸为$L$的一维系统中感测高达$R = pL/2$的畴尺寸。对于截止因子$p$ \to 0 $, the dynamics is Ising like and the domains grow with time $ t $ diffusively as $ t^{1/z} $ with $ z=2 $, while for $ p=1 $, the original model I showed ballistic dynamics with $ z \simeq 1 $. For intermediate values of $ p $, the domain growth, magnetisation and persistence show model I like behaviour up to a macroscopic crossover time $ t_1 \sim pL/2 $. Beyond $ t_1 $, characteristic power law variations of the dynamic …
