Thermal diode: Rectification of heat flux

By coupling two nonlinear one dimensional lattices, we demonstrate a thermal diode model that works in a wide range of system parameters. We provide numerical and analytical evidence for the underlying mechanism which allows heat flux in one direction while the system acts like an insulator when the temperature gradient is reversed. The possible experimental realization in nano scale systems is briefly discussed.Comment: 4 pages, 5 figs in publication for

Mode-coupling theory and molecular dynamics simulation for heat conduction in a chain with transverse motions

We study heat conduction in a one-dimensional chain of particles with longitudinal as well as transverse motions. The particles are connected by two-dimensional harmonic springs together with bending angle interactions. The problem is analyzed by mode-coupling theory and compared with molecular dynamics. We find very good, quantitative agreement for the damping of modes between a full mode-coupling theory and molecular dynamics result, and a simplified mode-coupling theory gives qualitative description of the damping. The theories predict generically that thermal conductance diverges as N^{1/3} as the size N increases for systems terminated with heat baths at the ends. The N^{2/5} dependence is also observed in molecular dynamics which we attribute to crossover effect.Comment: 17 pages, 13 figure

Heat conductivity in linear mixing systems

We present analytical and numerical results on the heat conduction in a linear mixing system. In particular we consider a quasi one dimensional channel with triangular scatterers with internal angles irrational multiples of pi and we show that the system obeys Fourier law of heat conduction. Therefore deterministic diffusion and normal heat transport which are usually associated to full hyperbolicity, actually take place in systems without exponential instability.Comment: Revtex, 4 pages, 6 EPS figure

Ballistic magneto-thermal transport in a Heisenberg spin chain at low temperatures

We study ballistic thermal transport in Heisenberg spin chain with nearest-neighbor ferromagnetic interactions at low temperatures. Explicit expressions for transmission coefficients are derived for thermal transport in a periodic spin chain of arbitrary junction length by a spin-wave model. Our analytical results agree very well with the ones from nonequilibrium Green's function method. Our study shows that the transmission coefficient oscillates with the frequency of thermal wave. Moreover, the thermal transmission shows strong dependence on the intrachain coupling, the length of the spin chain, and the external magnetic field. The results demonstrate the possibility of manipulating spin-wave propagation and magnetothermal conductance in the spin-chain junction by adjusting the intrachain coupling and/or the external magnetic field.Comment: 6 pages, 7 figure

Heat generation and transport due to time-dependent forces

We study heat transport for solids in the presence of arbitrary time-dependent force. Using nonequilibrium Green's function (NEGF) approach we present an exact analytical expression of current for the linear system. We found that the heat current can be expressed in terms of the displacement of the atoms in the center and the self energy of the baths. We carry out the calculation for the oscillatory driven force and study the steady state properties for one-dimensional linear chain and two-dimensional square lattice. We found that the heat current is related to the density of states of the system and is independent of the bath temperature in ballistic transport. The baths absorb energy only when their intrinsic frquency resonates with the applied frequency We also generalize the problem for multiple heat baths with different temperatures. We also discuss the effect due to nonlinear interactions in the center.Comment: v2 : 9 pages, 9 figure

Elastic and non-linear stiffness of graphene: a simple approach

The recent experiment [Science \textbf{321}, 385 (2008)] on the Young's modulus and third-order elastic stiffness of graphene are well explained in a very simple approach, where the graphene is described by a simplified system and the force constant for the non-linear interaction is estimated from the Tersoff-Brenner potential.Comment: 4 pages, 4 figure

Negative differential thermal resistance and thermal transistor

We report on the first model of a thermal transistor to control heat flow. Like its electronic counterpart, our thermal transistor is a three-terminal device with the important feature that the current through the two terminals can be controlled by small changes in the temperature or in the current through the third terminal. This control feature allows us to switch the device between "off" (insulating) and "on" (conducting) states or to amplify a small current. The thermal transistor model is possible because of the negative differential thermal resistance.Comment: 4 pages, 4 figures. SHortened. To appear in Applied Physics Letter

Isotopic effects on the thermal conductivity of graphene nanoribbons: localization mechanism

Thermal conductivity of graphene nanoribbons (GNR) with length 106~{\AA} and width 4.92~{\AA} after isotopic doping is investigated by molecular dynamics with quantum correction. Two interesting phenomena are found: (1) isotopic doping reduces thermal conductivity effectively in low doping region, and the reduction slows down in high doping region; (2) thermal conductivity increases with increasing temperature in both pure and doped GNR; but the increasing behavior is much more slowly in the doped GNR than that in pure ones. Further studies reveal that the physics of these two phenomena is related to the localized phonon modes, whose number increases quickly (slowly) with increasing isotopic doping in low (high) isotopic doping region.Comment: 6 fig