arXiv subjects

Moladad Nikbakht

Publications and source records attributed to Moladad Nikbakht.

7 recordsLinked to original sources

arXiv2023

Topological Edge States in Nanoparticle Chains: Isolating Radiative Heat Flux

Recent advancements in the field of topological band theory have significantly contributed to our understanding of intriguing topological phenomena observed in various classical and quantum systems, encompassing both wave and dissipative systems. In this study, we employ the notion of band theory to establish a profound connection between the spatio-temporal evolution of temperatures and the underlying topological properties of radiative systems. These systems involve the exchange of energy through radiation among a collection of particles. By utilizing the eigenstates of the response matrix of the system, we establish a robust framework for the examination of topological properties in radiative systems, considering both symmetric and asymmetric response matrices. Our formalism is specifically applied to investigate the topological phase transition in a one-dimensional chain composed of an even number of spherical nanoparticles. We provide compelling evidence for the existence and robustness of topological edge states in systems characterized by an asymmetric response matrix. Moreover, we demonstrate that by manipulating the arrangement and volume of particles, it is possible to control the system's structure and achieve desired topological features. Interestingly, we showed that the radiative heat transfer can be controlled and prevented by topological insulation. Additionally, we conduct an analysis of the temperature dynamics and the associated relaxation process in the proposed system. Our research findings demonstrate that the interplay between bulk states and localized states is pivotal in the emergence of distinct eigenstates and provides significant insights into the spatio-temporal dynamics of temperature and the process of thermalization within a system.

physics.optics↗

arXiv2021

Radiative thermal rectification in many-body systems

Radiative thermal diodes based on two-element structures rectify heat flows thanks to a temperature dependence of material optical properties. The heat transport asymmetry through these systems, however, remains weak without a significant change in material properties with the temperature. Here we explore the heat transport in three-element radiative systems and demonstrate that a strong asymmetry in the thermal conductance can appear because of many-body interactions, without any dependence of optical properties on the temperature. The analysis of transport in three-body systems made with polar dielectrics and metallic layers reveals that rectification coefficients exceeding 50 % can be achieved in the near-field regime with temperature differences of about 200 K. This work paves the way for compact devices to rectify near field radiative heat fluxes over a broad temperature range and could have important applications in the domain of nanoscale thermal management.

cond-mat.mes-hall↗

arXiv2021

Linear and nonlinear response for radiative heat transfer in many-body systems

A theory of temperature dynamics in many-body systems driven by time-dependent external sources is introduced. The formalism based on the combination of the perturbation theory and the fluctuational-electrodynamics approach in many-body systems. By using response theory, explicit formula for the temperature and phase shifts is derived and expressed in terms of the amplitude and phase of external power sources. Although the proposed method is highly efficient because it can skip the transient response, it is valid when external powers are weak. As an illustration of this theoretical framework, we have shown the dynamics of temperatures in one, two, and three degree of freedom systems driven by sine wave input powers. Finally, we highlighted some emergent phenomena arising from purely dynamical many-body effects, including amplification, attenuation, delaying or accelerating temperature responses. This work could find important applications in the domain of dynamical thermal management at the nanoscale.

cond-mat.mes-hall↗

arXiv2018

Radiative Heat Transfer Between Core-Shell Nanoparticles

Radiative heat transfer in systems with core-shell nanoparticles may exhibit not only a combination of disparate physical properties of its components but also further enhanced properties that arise from the synergistic properties of the core and shell components. We study the thermal conductance between two core-shell nanoparticles (CSNPs). The contribution of electric and magnetic dipole moments to the thermal conductance depend sensitively on the core and shell materials, and adjustable by core size and shell thickness. We predict that the radiative heat transfer in a dimer of Au@SiO2 CSNPs (i.e., silica-coated gold nanoparticles) could be enhanced several order of magnitude compared to bare Au nanoparticles. However, the reduction of several orders of magnitude in the heat transfer is possible between SiO2@Au CSNPs (i.e., silica as a core and gold as a shell) than that of uncoated SiO2 nanoparticles.

physics.app-ph↗

arXiv2017

Radiative Heat Transfer in Fractal Structures

The radiative properties of most structures are intimately connected to the way in which their constituents are ordered on the nano-scale. We have proposed a new representation for radiative heat transfer formalism in many-body systems. In this representation, we explain why collective effects depend on the morphology of structures, and how the arrangement of nanoparticles and their material affects the thermal properties in many-body systems. We investigated the radiative heat transfer problem in fractal (i.e., scale invariant) structures. In order to show the effect of the structure morphology on the collective properties, the radiative heat transfer and radiative cooling are studied and the results are compared for fractal and non-fractal structures. It is shown that fractal arranged nanoparticles display complex radiative behavior related to their scaling properties. we showed that, in contrast to non-fractal structures, heat flux in fractals is not of large-range character. By using the fractal dimension as a means to describe the structure morphology, we present a universal scaling behavior that quantitatively links the structure radiative cooling to the structure gyration radius.

cond-mat.mes-hall↗

arXiv2016

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.

cond-mat.mes-hall↗

arXiv2015

Three-body radiation dynamics in systems with anisotropic nanoparticles

The time evolution of temperatures of anisotropic nanoparticles in two and three-body systems are simulated for various relative orientations. Nanoparticles are immersed in a thermal bath at constant temperature. It is shown that in two-body systems, the relative orientation of nanoparticles could drastically affect the dynamics of temperature evolution and thermalization time scale. Moreover, in some configurations, the temperature difference in initial state has a minor effect on the dynamics of temperatures. In three-body systems, the orientation of the third nanoparticle influences the temperature dynamics, which allows one to control the thermalization time scales between anisotropic nanoparticles. Also, in addition to previously known contribution of the smallest distance between isotropic nanoparticles on the thermalization time scales, it is shown that the nanoparticles' orientations are more important in some particular arrangements.

cond-mat.mes-hall↗