Negative Differential Thermal Resistance Research Articles

One-Dimensional van der Waals Heterojunction Comprising Carbon Nanotube Half-Wrapped in Boron Nitride Nanotube: Deep Investigation of Thermal Rectification.

One-dimensional van der Waals (vdWs) heterostructures are celebrated for their exceptional thermal management capabilities, garnering significant research interest. Consequently, our research focused on the one-dimensional vdWs heterojunction comprising carbon nanotube half-wrapped in boron nitride nanotube (BNCNT), specifically their thermal rectification (TR) properties. We employed non-equilibrium molecular dynamics to explore the TR mechanism and assess the impacts of temperature, strain, and coupling strength on heat flux and TR ratio. Our findings reveal that the backward heat flux demonstrates greater atomic vibration instability, as indicated by mean square displacement (MSD), compared to forward heat flux. This instability leads to a higher concentration of localized phonons, thereby diminishing the backward heat flux and enhancing TR. Additionally, we utilized MSD to shed light on the negative differential thermal resistance phenomenon and the influence of stress on forward and backward heat fluxes. Remarkably, TR ratios reached 344% at 3% strain and 400% at -1% strain. Calculations of phonon density of states revealed a competitive mechanism between in-plane and out-of-plane phonons coupling in the inner carbon nanotube and an overlap degree of out-of-plane phonon spectra between the inner carbon nanotube and outer boron nitride nanotube. This accounts for the differing trends in forward and backward heat fluxes as coupling strength χ increases, with TR ratios exceeding 1000% at χ = 7.5. This study provides vital insights for advancing one-dimensional vdWs thermal rectifiers.

Modeling and Analysis of a Radiative Thermal Memristor

This study presents a theoretical framework for a radiative thermal memristor (RTM), utilizing Tungsten-doped vanadium dioxide (WVO) as the phase-change material (PCM) and silicon carbide (SiC) in the far-field regime. The behavior of the RTM is depicted through a Lissajous curve, illustrating the relationship between net flux (Q) and a periodically modulated temperature difference ΔT(t). It is established that temperature variations in the memristance (M) of the RTM form a closed loop, governed by PCM hysteresis. The analysis explores the impact of thermal conductivity contrast (r) and periodic thermal input amplitude (θ) on the Q–ΔT curve and the M–ΔT curve and negative differential thermal resistance (NDTR), revealing notable effects on the curve shapes and the emergence of NDTR. An increasing r leads to changes in the Lissajous curve’s shape and enhances the NDTR influence, while variations in both r and (θ) significantly affect the Q values and Lissajous curve amplitudes. In the M–ΔT curve, the height is linked to thermal conductivity contrast (r), with increasing r resulting in higher curve heights.

Optimizing the performance of the thermal transistor based on negative differential thermal resistance

Thermal transistors have significant potential in thermal management due to their ability to precisely control the heat fluxes. However, the current design has a limited working temperature range and cannot meet the demand for heat control. In this work, we optimize the performance of a thermal transistor based on negative differential thermal resistance using a modified Lorentz gas model, focusing on the effects of gate control and thermal conductance. We find that the control of the gate has an asymmetrical property, and the sufficient control can expand the working region by more than 1.5 times. In addition, the switching and amplifying functions of the thermal transistor are inversely dependent on thermal conductance, and an increase in thermal conductance can lead to a 27 times amplification in heat flux. The synergistic regulation of the two factors results in the optimal performance of a 44% working region and a 33 times amplification in heat flux. These findings refresh the understanding of the performance limits of thermal transistors, promoting efficient thermal management and addressing heat dissipation issues.

Analytical expression of negative differential thermal resistance in a macroscopic heterojunction

Heat flux (J) generally increases with temperature difference in a material. A differential coefficient of J against temperature (T) is called differential thermal conductance (k), and an inverse of k is differential thermal resistance (r). Although k and r are generally positive, they can be negative in a macroscopic heterojunction with positive T-dependent interfacial thermal resistance (ITR). The negative differential thermal resistance (NDTR) effect is an important effect that can realize thermal transistor, thermal memory, and thermal logic gate. In this paper, we examine analytical expressions of J, k, r, and other related quantities as a function of parameters related to thermal conductivity (κ) and ITR in a macroscopic heterojunction to precisely describe the NDTR effect.

Prediction of high thermal rectification behavior in carbon/C3N heteronanotubes based on nonequilibrium molecular dynamics simulations.

Carbon/C3N heteronanotubes (CC3NNTs) have garnered significant interest for their distinctive performance and versatility across various applications. However, the understanding of interfacial heat transport within these heterostructures remains limited. This study aims to enrich the field by constructing models of CC3NNTs through the bonding of CNTs and C3NNTs, and employs nonequilibrium molecular dynamics (NEMD) simulations to predict their heat flux and thermal rectification (TR) effects. Placing the heat source in the CNT region induces a stronger heat flux compared to the C3NNT region, thus demonstrating a pronounced TR effect. This effect can be attributed to the mismatch in phonon spectra, as evidenced by the cumulative correlation factor derived from the phonon density of states (phonon DOS). Using this approach, we predict that the TR ratio for zigzag CC3NNTs (ZCC3NNT) significantly exceeds that of armchair CC3NNTs (ACC3NNT). Notably, in contrast to ACC3NNT, ZCC3NNT exhibits the phenomenon of negative differential thermal resistance in the backward heat flux with a temperature difference of Δ = 120 K. This phenomenon can be attributed to a lower phonon participation ratio at Δ = 120 K compared to other values of Δ. Subsequently, given that ZCC3NNT demonstrates the most pronounced TR ratio at room temperature, we explored how stress-strain, system size, defect density, and interface position impact the TR ratio. These insights are invaluable for guiding the design of thermal rectifiers, smart thermal management systems, and microelectronic processor coolers.

Thermal rectification in mass-asymmetric one-dimensional anharmonic oscillator lattices with and without a ballistic spacer

In this work we perform a systematic analysis of various structural parameters that have influence on the thermal rectification effect, i.e. asymmetrical heat flow, and the negative differential thermal resistance —reduction of the heat flux as the applied thermal bias is increased— present in a one-dimensional, segmented mass-graded system consisting of a coupled nearest-neighbor harmonic oscillator lattice (ballistic spacer) and two diffusive leads (modeled by a substrate potential) attached to the lattice at both boundaries. At variance with previous works, we consider the size of the spacer as smaller than that of the leads. Also considered is the case where the leads are connected along the whole length of the oscillator lattice; that is, in the absence of the ballistic spacer. Upon variation of the system’s parameters it was determined that the performance of the device, as quantified by the spectral properties, is largely enhanced in the absence of the ballistic spacer for the small system-size limit herein considered.

Macroscopic negative differential thermal resistance in the overlapping graphene homojunction structure

As one of the most potential ways to manipulate heat, thermal functional devices have achieved several breakthroughs in recent years, but are still limited to theoretical simulations. One of its theoretical bases is the existence of the negative differential thermal resistance (NDTR). However, most of the existing systems where the phenomenon of NDTR is found are atomic-level systems. In order to realize the macroscopic NDTR and provide effective theoretical guidance and support for the practical realization of thermal functional devices, we construct the overlapping graphene homojunction model, using the negative thermal expansion property of graphene to modify the overlapping area, and thus regulating the heat flow. The COMSOL-MATLAB co-simulation is used to perform calculations through negative feedback loops. It is found that the NDTR phenomenon exists under certain parameter conditions, which can provide new ideas and bring more opportunities for the experimental realization of nonlinear thermal functional devices.

A high-performance thermal transistor based on interfacial negative differential thermal resistance

A thermal transistor, which can achieve the smart, flexible, and precisely controlled thermal management, proves to be a promising thermal device. Recently, thermal transistors based on the negative differential thermal resistance (NDTR) have been regarded as the most feasible configuration considering their simple structures. Among the several methods to implement NDTR, the method of reducing the contact pressure between mated surfaces by using the negative thermal expansion material, thus generating a negative temperature dependent interface thermal conductance and accompanied NDTR, is the most likely to be observed experimentally. In this paper, a thermal transistor based on NDTR is designed by engineering the interfacial thermal resistance. Moreover, we optimize the switching function and the amplification function of the transistor by only adjusting the temperature and the length of the source terminal. As an example, a silicon thermal transistor with a high switching ratio as well as an accurately controlled thermal flux amplification function is discussed at low temperature. The design and optimization of macroscopic thermal transistor will promote the rapid development of thermal functional devices and help to control thermal flux in a more flexible and effective way.

Stochastic dynamics of a nonlinear thermal circuit with bistability.

Stochastic dynamics of a nonlinear thermal circuit is studied. Due to the existence of negative differential thermal resistance, there exist two stable steady states that satisfy both the continuity and stability conditions. The dynamics of such a system is governed by a stochastic equationwhich describes originally an overdamped Brownian particle that undergoes a double-well potential. Correspondingly, the finite time temperature distribution takes a double-peak profile and each peak is approximately Gaussian. Owing to the thermal fluctuation, the system is able to jump occasionally from one stable steady state to the other. The probability density distribution of the lifetime τ for each stable steady state follows a power-law decay τ^{-3/2} in the short-τ regime and an exponential decay e^{-τ/τ_{0}} in the long-τ regime. All these observations can be well explained analytically.

Phononic thermal rectifier: a new proposition

We put forward a new proposition for achieving a phonon-based thermal rectifier at the nanoscale level, considering a one-dimensional phononic system. The central mechanism relies on the temperature-dependent spring constant along with the presence of mass modulation which essentially breaks the symmetry in the system and thus leads to different thermal currents in two bias polarities. Along with thermal rectification, the phenomenon of negative differential thermal resistance (NDTR) is also observed. The NDTR effect is utilized further to have the NOT gate operation. The present analysis may open up new possibilities for designing efficient thermal rectifiers and logic gates.

Negative differential thermal resistance effect in a nanoscale sandwiched system with nanostructured surfaces

In this work, the negative differential thermal resistance effect has been proposed in a solid-liquid-solid sandwiched system with a nanostructured cold surface. Non-equilibrium molecular dynamics simulations demonstrate that the heat flux in the present sandwiched system increases with the temperature bias for low temperature bias, while for high temperature bias, the heat flux decreases counter-intuitively with increasing temperature bias. Based on the analysis of the interfacial thermal resistance and the density depletion length at the solid-liquid interface, the negative differential thermal resistance effect at high temperature bias is attributed to the suppressed solid-liquid interfacial thermal conductance with decreasing temperature. In addition, it is found that the negative differential thermal resistance effect can be tuned by the size of the nanostructure.

Negative differential thermal resistance of fluids induced by heat baths

It has recently been shown that in one-dimensional hard-point gases, there is a mechanism that induces negative differential thermal resistance (NDTR) between heat baths. We examine this mechanism in more general higher-dimensional fluids described by multiparticle collision dynamics. We consider fluids in a finite cuboid region of three-dimensional space with each end in contact with a heat bath. Based on analytical results and numerical models, we find that the mechanism underlying NDTR also works for high-dimensional fluidic systems with weak interactions and is very robust to mixed fluids. Our results significantly advance knowledge of NDTR induced by heat baths and illuminate different directions to explore in fabricating fluid thermal transistors in micro- and nanosystems.

Interlayer coupling-induced controllable negative differential thermal resistance in graphene/h-BN van der Waals heterostructure

The van der Waals (vdW) heterostructures employing graphene and hexagonal boron nitride (h-BN) have emerged as a typical system for building emergent two-dimensional devices, such as atomically thin transistors or capacitors. Herein, we study the nonlinear thermal transport in such vdW heterostructure by non-equilibrium molecular dynamics simulations. The results show that an obvious negative differential thermal resistance (NDTR) phenomenon can be observed under small temperature bias when the interlayer coupling becomes stronger. The vibrational spectra analysis manifests that the phonon filtering mechanism induced by interlayer coupling greatly hinders the interfacial thermal transport. To obtain the optimum conditions, the dependence of NDTR on the system length, lateral width, external temperature, and defect density is taken into account. Our findings extend the phonon filtering mechanism to thermal information processing.

Tunable Thermal Rectification and Negative Differential Thermal Resistance in Gas-Filled Nanostructure with Mechanically-Controllable Nanopillars

Tunable Thermal Rectification and Negative Differential Thermal Resistance in Gas-Filled Nanostructure with Mechanically-Controllable Nanopillars

Negative differential thermal resistance in a two-dimensional gas model

The negative differential thermal resistance (NDTR) effect refers to a phenomenon that may take place in a heat transport system where the heat current counterintuitively decreases as the temperature difference between heat baths increases. Understanding and controlling the NDTR properties of out-of-equilibrium systems and using them to design new functional thermal devices are the major challenges of modern science and technology, which has important theoretical significance and application prospects. Up to now, the various lattice models representing solid materials have been taken to study the NDTR properties, but the fluid models have not received enough attention. It has recently been shown that in one-dimensional hard-point gas models representing fluids, there is a mechanism for NDTR induced by heat baths. The mechanism for NDTR in such a system depends on the simple fact that decreasing the temperature of the cold bath can weaken the motion of particles and decrease the collision rate between particles and the hot bath, thus impeding thermal exchange between the cold and hot baths. In this paper, we study how this mechanism works in more general two-dimensional gas models described by multi-particle collision dynamics. The gas models we consider are in a finite rectangular region of two-dimensional space with each end in contact with a heat bath. Based on the analytical results and numerical simulations, we show that the mechanism underlying NDTR induced by heat baths is also in effect for two-dimensional gas models and is applicable for describing systems with small sizes and weak interactions. Our result, together with that previously obtained in one-dimensional gas models, provides strong evidence that gas systems can exhibit NDTR by decreasing the temperature of the heat bath, which sheds new light on the exploring direction for developing various fluidic thermal control devices.

Negative Differential Thermal Resistance Effect in a Nanoscale Sandwiched System with Nanostructured Surfaces

Negative Differential Thermal Resistance Effect in a Nanoscale Sandwiched System with Nanostructured Surfaces

Bidirectional and Unidirectional Negative Differential Thermal Resistance Effect in a Modified Lorentz Gas ModelSupported by the National Natural Science Foundation of China (Grant Nos. 11975125 and 21803031), the Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant No. KYCX20 1229), and the Natural Science Foundation of the Jiangsu Higher Education Institution of China (Grant No. 18KJB150022).

Recently, the negative differential thermal resistance effect was discovered in a homojunction made of a negative thermal expansion material, which is very promising for realizing macroscopic thermal transistors. Similar to the Monte Carlo phonon simulation to deal with grain boundaries, we introduce positive temperature-dependent interface thermal resistance in the modified Lorentz gas model and find negative differential thermal resistance effect. In the homojunction, we reproduce a pair of equivalent negative differential thermal resistance effects in different temperature gradient directions. In the heterojunction, we realize the unidirectional negative differential thermal resistance effect, and it is accompanied by the super thermal rectification effect. Using this new way to achieve high-performance thermal devices is a new direction, and will provide extensive reference and guidance for designing thermal devices.

Brownian thermal control device

Here, we design a Brownian thermal control device with microscale, which consists of two compartments modeled by two spatially periodic potentials, respectively. Through calculating its thermal current, it is found that the device can play roles of both thermal diode and thermal on–off, depending on its symmetry and amplitudes and spatial frequencies of the periodic potentials. In the case of optimal amplitudes and spatial frequencies, a negative differential thermal resistance effect also appears in the system, by means of which a Brownian thermal transistor can be developed. These findings have an important significance for understanding operating mechanisms through which some nano-scale machines and organisms usually work under environments of constant temperatures.

Negative differential thermal resistance effect in a macroscopic homojunction

The negative differential thermal resistance (NDTR) effect is an important mechanism to realize a thermal transistor that is of great significance to realize thermal control. We find that with accompanying an interface thermal resistance (ITR), which has a certain temperature-dependence, the macroscopic homojunction can present a NDTR. The temperature-dependent ITR to achieve NDTR can be realized by using materials with negative thermal expansion. As an example, a NDTR in the silicon homojunction was found at low temperature. The discovery of macro-NDTR will pave the way to design a macroscopic thermal transistor and also help us manipulate thermal flow more freely and effectively.

Enhanced Effect of Negative Differential Thermal Resistance in Nanoscale Confined Structure with Nanopatterned Surfaces

A nanoscale confined fluid structure with nanopatterned surface has been investigated by using nonequilibrium molecular dynamics simulations and kinetic theory. The negative differential thermal re...