Heat Transfer Through Near-Field Interactions in Nanofluids

Interlayer Heat Transfer in Bilayer Carrier Systems

We study theoretically how energy and heat are transferred between the two-dimensional layers of bilayer carrier systems due to near-field interlayer carrier interaction. We derive general expressions for the interlayer heat transfer and thermal conductance. Approximation formulas and detailed calculations for semiconductor and graphene based bilayers are presented. Our calculations for GaAs, Si and graphene bilayers show that the interlayer heat transfer can exceed the electron-phonon heat transfer below (system dependent) finite crossover temperature. We show that disorder strongly enhances …

Electric field effect in heat transfer in 2D devices

We calculate heat transfer between a 2D sheet (e.g. graphene) and a dielectric in presence of a gate voltage. The gate potential induces surface charge densities on the sheet and dielectric, which results in electric field, which is coupled to the surface displacements and, as a consequence, resulting an additional contributions to the radiative heat transfer. The electrostatic and van der Waals interactions between the surface displacement result in the phonon heat transfer, which we calculate taking into account the nonlocality of these interactions. Numerical calculations are presented for …

Shape-dependence of near-field heat transfer between a spheroidal nanoparticle and a flat surface

We study the radiative heat transfer between a spheroidal metallic nanoparticle and a planar metallic sample for near- and far-field distances. In particular, we investigate the shape dependence of the heat transfer in the near-field regime. In comparison with spherical particles, the heat transfer typically varies by factors between 1/2 and 2 when the particle is deformed such that its volume is kept constant. These estimates help to quantify the deviation of the actual heat transfer recorded by a near-field scanning thermal microscope from the value provided by a dipole model which assumes a…

Radiative Heat Transfer in Anisotropic Many-Body Systems: Tuning and Enhancement

A general formalism for calculating the Radiative Heat Transfer in many body systems with anisotropic component is presented. Our scheme extends the theory of radiative heat transfer in isotropic many body systems to anisotropic cases. In addition, the radiative heating of the particles by the thermal bath is taken into account in our formula. It is shown that the radiative heat exchange (HE) between anisotropic particles and their radiative cooling/heating (RCH) could be enhanced several order of magnitude than that of isotropic particles. Furthermore, we demonstrate that both the HE and RCH …

General formulation of coupled radiative and conductive heat transfer between compact bodies

We present a general framework for studying strongly coupled radiative and conductive heat transfer between arbitrarily shaped bodies separated by sub-wavelength distances. Our formulation is based on a macroscopic approach that couples our recent fluctuating volume--current (FVC) method of near-field heat transfer to the more well known Fourier conduction transport equation. We apply our technique to consider heat exchange between aluminum-zinc oxide nanorods and show that the presence of bulk plasmon resonances can result in extremely large radiative heat transfer rates (roughly twenty times…

Near-field radiative heat transfer and van der Waals friction between closely spaced graphene and amorphous SiO$_2$

We study the radiative heat transfer and the van der Waals friction between graphene and an amorphous SiO$_2$ substrate. We study the surface phonon-polaritons contribution to the low-field mobility as a function of temperature and of carrier density. We find that the electric current saturate at a high electric field, in agreement with experiment. The saturation current depends weakly on the temperature, which we attribute to the "quantum" friction between the graphene carriers and the substrate optical phonons. We calculate the frictional drag between two graphene sheets caused by van der Wa…

Near-field radiative heat transfer between closely spaced graphene and amorphous SiO$_2$

We study the near-field radiative energy transfer between graphene and an amorphous SiO$_2$ substrate. In comparison with the existing theories of near-field radiative heat transfer our theory takes into account that the free carriers in graphene are moving relative to the substrate with a drift velocity $v$. In this case the heat flux is determined by both thermal and quantum fluctuations. We find that quantum fluctuations give an important contribution to the radiative energy transfer for low temperatures and high electric field (large drift velocities). For nonsuspended graphene the near-fi…

Near-field heat transfer between disordered conductors

We study heat transfer mediated by near-field fluctuations of the electromagnetic field. In case of metals the latter are dominated by Coulomb interactions between thermal fluctuations of electronic density. We show that an elastic scattering of electrons, leading to diffusive propagation of density fluctuations, results in a qualitative change of the radiation law. While the heat flux between clean metals follows the Stefan-Boltzmann-like $T^4$ dependence, the heat exchange between disordered conductors is significantly enhanced and scales as $T^3$ at low temperatures.

Heat transfer statistics in extreme-near-field radiation

We investigate the full counting statistics of extreme-near-field radiative heat transfer using nonequilibrium Green's function formalism. In the extreme near field, the electron-electron interactions between two metallic bodies dominate the heat transfer process. We start from a general tight-binding electron Hamiltonian and obtain a Levitov-Lesovik like scaled cumulant generating function (SCGF) using random phase approximation to deal with electron-electron interaction. The expressions of heat current and its fluctuation (second cumulant) are obtained from the SCGF. The fluctuation symmetry…

Contribution of the acoustic waves to near-field heat transfer

Calculations of the radiative and phonon heat transfer between metals in an extreme near field in presence of electrostatic potential difference are given. Potential difference leads to a coupling between the radiation field and acoustic waves in solid, as a result of which the heat flux between two gold plates associated with p -polarized electromagnetic waves increases by many orders of magnitude as the potential difference varies from 0 to 10V. The radiative heat transfer is compared with the phonon heat transfer associated with the electrostatic and van der Waals interactions between the s…

Resonant supercollisions and electron-phonon heat transfer in graphene

We study effects of strong impurities on the heat transfer in a coupled electron-phonon system in disordered graphene. A detailed analysis of the electron-phonon heat exchange assisted by such an impurity through the 'resonant supercollision' mechanism is presented. We further explore the local modification of heat transfer in a weakly disordered graphene due to a resonant scatterer and determine spatial profiles of the phonon and electron temperature around the scatterer under electrical driving. Our results are consistent with recent experimental findings on imaging resonant dissipation from…

Van der Waals force assisted heat transfer for vacuum gap spacings

Phonons (collective atomic vibrations in solids) are more effective in transporting heat than photons. This is the reason why the conduction mode of heat transport in nonmetals (mediated by phonons) is dominant compared to the radiation mode of heat transport (mediated by photons). However, since phonons are unable to traverse a vacuum gap (unlike photons) it is commonly believed that two bodies separated by a gap cannot exchange heat via phonons. Recently, a mechanism was proposed by which phonons can transport heat across a vacuum gap - through Van der Waals interaction between two bodies wi…

复合费米子双层结构中的近场传热与拖曳电阻

Near-field heat transfer and drag resistance in bilayers of composite fermions

该研究针对关联复合费米子量子液体电子双层系统的近场传热问题，基于陈-西蒙斯规范理论计算多区域层间热导，分析等离激元增强效应，并给出偶分母分数量子霍尔态下传热电导与拖曳电阻的关联。

Electric double layer effect in an extreme near-field heat transfer between metal surfaces

Calculations of heat transfer between two plates of gold in an extreme near field is performed taking into account the existence of the electric double layer on metal surfaces. For d < 3nm the double layer contribution exceeds the predictions of the conversional theory of the heat transfer by several orders of magnitudes. This effect is due to a coupling between the radiation electric field and the double layer dipole moment. The results obtained can be used for the heat management at the nanoscale by intentionally changing the parameters of surface dipoles with the help of engineering.

Coupling between conduction and near-field radiative heat transfer in tip-plane geometry

We analyze the coupling between conduction and radiative heat transfer in near-field regime between two coaxial cylinders separated by a vacuum gap. By solving the heat transport equation in the steady-state regime between metals or polar materials we highlight a flux saturation mechanism for the radiative transfer even without non-local effect. In the case of polar materials this saturation occurs in the separation distances range of 1 to 10 nm which can be experimentally explored.

Amplifying thermal conduction calibre of nanocolloids employing induced electrophoresis

Electrophoresis has been shown as a novel methodology to enhance heat conduction capabilities of nanocolloidal dispersions. A thoroughly designed experimental system has been envisaged to solely probe heat conduction across nanofluids by specifically eliminating the buoyancy driven convective component. Electric field is applied across the test specimen in order to induce electrophoresis in conjunction with the existing thermal gradient. It is observed that the electrophoretic drift of the nanoparticles acts as an additional thermal transport drift mechanism over and above the already existent…

Radiative heat transfer between nanoparticles: shape dependence and three-body effect

We study the effect of particles shape on the radiative heat transfer in a three-body system. It is found that the radiative heat flux between two nanoparticles in a three body system can be tuned by the shape of the third particle. In particular, we show that the heat flux is very sensitive to the particle shapes and slight mismatches of shapes results in either enhanced or suppressed heat flux.

Dynamics of heat transfer between nano systems

We develop a dynamical theory of heat transfer between two nano systems. In particular, we consider the resonant heat transfer between two nanoparticles due to the coupling of localized surface modes having a finite spectral width. We model the coupled nanosystem by two coupled quantum mechanical oscillators, each interacting with its own heat bath, and obtain a master equation for the dynamics of heat transfer. The damping rates in the master equation are related to the lifetimes of localized plasmons in the nanoparticles. We study the dynamics towards the steady state and establish connectio…

跨维度等离激元薄膜系统中的远场与近场热传递

Far- and Near-Field Heat Transfer in Transdimensional Plasmonic Film Systems

本文对比非局域与局域Drude模型，研究跨维度等离激元薄膜的热传递，发现非局域模型可增强近场热流并提升对超薄膜辐射热传递的理解。

Radiative heat transfer between dielectric bodies

The recent development of a scanning thermal microscope (SThM) has led to measurements of radiative heat transfer between a heated sensor and a cooled sample down to the nanometer range. This allows for comparision of the known theoretical description of radiative heat transfer, which is based on fluctuating electrodynamics, with experiment. The theory itself is a macroscopic theory, which can be expected to break down at distances much smaller than 10-8m. Against this background it seems to be reasonable to revisit the known macroscopic theory of fluctuating electrodynamics and of radiative h…

由库仑相互作用介导的跨电容耦合硅纳米点的单电子热传递统计

Coulomb-mediated single-electron heat transfer statistics across capacitively coupled silicon nanodots

研究通过实验量化纳米尺度库仑介导热传递统计，为随机热力学和非平衡态普遍关系提供新视角。

Influence of roughness on near-field heat transfer between two plates

The surface roughness correction to the near-field heat transfer between two rough bulk materials is discussed by using second-order perturbation theory. The results allow for estimating the impact of surface roughness to the heat transfer in recent experiments between two plates and between a microsphere and a plate (using the Derjaguin approximation). Furthermore, we show that the proximity approximation for describing rough surfaces is valid for distances much smaller than the correlation length of the surface roughness even if the heat transfer is dominated by the coupling of surface modes…

Perspective on Near-Field Radiative Heat Transfer

Although near-field radiative heat transfer was introduced in the 1950's, interest in the field has recently revived, as the effect promises improved performance in various applications where contactless temperature regulation in the small-scale is a requirement. With progress in computational electromagnetics as well as in nanoinstrumentation, it has become possible to simulate the effect in complex configurations and to measure it with high precision. In this Perspective, we highlight key theoretical and experimental advances in the field, and we discuss important developments in tailoring a…

Reply to "On the heat transfer across a vacuum gap mediated by Casimir force"

In a recent paper (arXiv:2003.00760) and a related article (Z. Naturforsch. A 75, 803-807), S.-A. Biehs et al. present erroneous interpretations of our work on the heat transfer driven by Casimir force. Here, we clarify several key concepts and refute their claims.

Plasmonic Tuning of the Near Field Heat Transfer in Double Layer Graphene

We discuss the non-radiative heat transfer in non-equilibrium double layer graphene system. We show that at the neutrality point the heat exchange is dominated by the inter-layer plasmon modes and derive analytic expressions for the heat current as a function of temperature and the interlayer separation. These results show that for a range of low temperatures the two graphene layers are much more efficient heat exchanger than conventional metals. The physical reason behind this phenomenon is the presence of inter-band excitations with a large energy, and a small momentum in graphene spectrum. …

Control of near-field radiative heat transfer based on anisotropic 2D materials

In this work, we study the near-field radiative heat transfer between two suspended sheets of anisotropic 2D materials. It is found that the radiative heat transfer can be enhanced with orders-of-magnitude over the blackbody limit for nanoscale separation. The enhancement is attributed to the excitation of anisotropic and hyperbolic plasmonic modes. Meanwhile, a large thermal modulation effect, depending on the twisted angle of principal axes between the upper and bottom sheets of anisotropic 2D materials, is revealed. The near-field radiative heat transfer for different concentrations of elec…

Theoretical constraints on reciprocal and non-reciprocal many-body radiative heat transfer

We study the constraints on reciprocal and non-reciprocal many-body radiative heat transfer imposed by symmetry and the second law of thermodynamics. We show that the symmetry of such a many-body system in general forms a magnetic group, and the constraints of the magnetic group on the heat transfer can be derived using a generalized reciprocity theorem. We also show that the second law of thermodynamics provides additional constraints in the form of a nodal conservation law of heat flow at equilibrium. As an application, we provide a systematic approach to determine the existence of persisten…

Modulation of near-field heat transfer between two gratings

We present a theoretical study of near-field heat transfer between two uniaxial anisotropic planar structures. We investigate how the distance and relative orientation (with respect to their optical axes) between the objects affect the heat flux. In particular, we show that by changing the angle between the optical axes it is possible in certain cases to modulate the net heat flux up to 90% at room temperature, and discuss possible applications of such a strong effect.

Equivalent circuit model of radiative heat transfer

Here, we develop a theory of radiative heat transfer based on an equivalent electrical network representation for the hot material slabs in an arbitrary multilayered environment with arbitrary distribution of temperatures and electromagnetic properties among the layers. Our approach is fully equivalent to the known theories operating with the fluctuating current density, while being significantly simpler in analysis and applications. A practical example of the near-infrared heat transfer through the micron gap filled with an indefinite metamaterial is considered using the suggested method. The…

Optomechanical heat transfer between molecules in a nanoplasmonic cavity

We explore whether localized surface plasmon polariton modes can transfer heat between molecules placed in the hot spot of a nanoplasmonic cavity through optomechanical interaction with the molecular vibrations. We demonstrate that external driving of the plasmon resonance indeed induces an effective molecule-molecule interaction corresponding to a new heat transfer mechanism, which can even be more effective in cooling the hotter molecule than its heating due to the vibrational pumping by the plasmon. This novel mechanism allows to actively control the rate of heat flow between molecules thro…

A mesoscopic description of radiative heat transfer at the nanoscale

We present a formulation of the nanoscale radiative heat transfer (RHT) using concepts of mesoscopic physics. We introduce the analog of the Sharvin conductance using the quantum of thermal conductance. The formalism provides a convenient framework to analyse the physics of RHT at the nanoscale. Finally, we propose a RHT experiment in the regime of quantized conductance.

Super-Planckian Far-Field Radiative Heat Transfer

We present a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. We illustrate this phenomenon with micron-sized structures that can be readily fabricated and tested with existing technology. Our work shows the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nano-devices.

Heat transfer between anisotropic nanopartricles: Enhancement and switching

We theoretically study heat transfer between two anisotropic nanoparticles in vacuum, and derive closed expressions in terms of the anisotropic dipole polarizabilities. We show that transfer between two small spheroids can be many times as large as the one for two spheres of same volumes. Such increase with anisotropy is also found for the heat emission of an isolated small spheroid. Furthermore, we observe a strong dependence of transfer on the relative orientation, yielding the interpretation as a heat transfer switch. The switch quality, given as the ratio of transfer in the ``on'' and ``of…