arXiv subjects

Daxing Xiong

Publications and source records attributed to Daxing Xiong.

23 records · Page 2Linked to original sources

arXiv2017

Heat perturbations spreading in the Fermi-Pasta-Ulam-$β$ system with next-nearest-neighbor coupling: Competition between phonon dispersion and nonlinearity

We employ the heat perturbations correlation function to study thermal transport in the one-dimensional (1D) Fermi-Pasta-Ulam-$β$ lattice with both nearest-neighbor and next-nearest-neighbor couplings. We find that such a system bears a peculiar phonon dispersion relation, and thus there exists a competition between phonon dispersion and nonlinearity that can strongly affect the heat correlation function' shape and scaling property. Specifically, for small and large anharmoncity, the scaling laws are ballistic and superdiffusive types, respectively, which are in good agreement with the recent theoretical predictions; whereas in the intermediate range of the nonlinearity, we observe an unusual multiscaling property characterized by a \emph{nonmonotonic} delocalization process of the central peak of the heat correlation function. To understand this multiscaling laws, we also examine the momentum perturbations correlation function and find a transition process with the same turning point of the anharmonicity as that shown in the heat correlation function. This suggests coupling between the momentum transport and the heat transport, in agreement with the theoretical arguments of mode cascade theory.

cond-mat.stat-mech↗

arXiv2017

Anomalous temperature-dependent heat transport in one-dimensional momentum-conserving systems with soft-type interparticle interaction

We here numerically investigate the heat transport behavior in a one-dimensional lattice with a soft-type (ST) anharmonic interparticle interaction. It is found that with the increase of system's temperature, while the introduction of ST anharmonicity softens phonons and decreases their velocities, this type of nonlinearity like its counterpart of hard type (HT), can still not be able to fully damp the longest wave phonons. Therefore, an anomalous temperature dependent heat transport with certain scaling properties similarly to those in the Fermi-Pasta-Ulam like systems with HT interactions can be seen. Our detailed examination from simulations well verify this temperature dependent behavior.

cond-mat.stat-mech↗

arXiv2016

Underlying mechanisms for normal heat transport in one-dimensional anharmonic oscillator systems with a double-well interparticle interaction

Previous studies have suggested a crossover from superdiffusive to normal heat transport in one-dimensional (1D) anharmonic oscillator systems with a double-well type interatomic interaction like $V(ξ)=-ξ^2/2+ξ^4/4$, when the system temperature is varied. In order to better understand this unusual manner of thermal transport, here we perform a direct dynamics simulation to examine how the spreading processes of the three physical quantities, i.e., the heat, the total energy and the momentum, would depend on temperature. We find three main points that are worth noting: (i) The crossover from superdiffusive to normal heat transport is well verified from a new perspective of heat spread; (ii) The spreading of the total energy is found to be very distinct from heat diffusion, especially that under some temperature regimes, energy is strongly localized, while heat can be superdiffusive. So one should take care to derive a general connection between the heat conduction and energy diffusion; (iii) In a narrow range of temperatures, the spreading of momentum implies clear unusual non-ballistic behaviors; however, such unusual transport of momentum cannot be directly related to the normal transport of heat. An analysis of phonons spectra suggests that one should also take the effects of phonons softening into account. All of these results may provide insights into establishing the connection between the macroscopic heat transport and the underlying dynamics in 1D systems.

cond-mat.stat-mech↗

arXiv2016

Crossover between different universality classes: Scaling for thermal transport in one dimension

For thermal transport in one-dimensional (1D) systems, recent studies have suggested that employing different theoretical models and different numerical simulations under different system's parameter regimes might lead to different universality classes of the scaling exponents. In order to well understand the universality class(es), here we perform a direct dynamics simulation for two archetype 1D oscillator systems with quite different phonon dispersions under various system's parameters and find that there is a crossover between the different universality classes. We show that by varying anharmonicity and temperatures, the space-time scaling exponents for the systems with different dispersions can be feasibly tuned in different ways. The underlying picture is suggested to be understood by phonons performing various kinds of continuous-time random walks (in most cases, be the Lévy walks but not always), probably induced by the peculiar phonon dispersions along with nonlinearity. The results and suggested mechanisms may provide insights into controlling the transport of heat in some 1D materials.

cond-mat.stat-mech↗

arXiv2011

The effect of discrete breathers on heat conduction in nonlinear chains

Intensive studies in the past decades have suggested that the heat conductivity $κ$ diverges with the system size $L$ as $κ\sim L^α$ in one dimensional momentum conserving nonlinear lattices and the value of $α$ is universal. But in the Fermi-Pasta-Ulam-$β$ lattices with next-nearest-neighbor interactions we find that $α$ strongly depends on $γ$, the ratio of the next-nearest-neighbor coupling to the nearest-neighbor coupling. We relate the $γ$-dependent heat conduction to the interactions between the long-wavelength phonons and the randomly distributed discrete breathers. Our results provide an evidence to show that the nonlinear excitations affect the heat transport.

cond-mat.stat-mech↗