arXiv subjects

Houssem Rezgui

Publications and source records attributed to Houssem Rezgui.

5 recordsLinked to original sources

arXiv2026

Phonon-Mediated Thermal Transport in Nanocrystalline Silicon Using Machine-Learning Interatomic Potentials

Understanding phonon-mediated heat transport in structurally complex materials remains a central challenge for next-generation electronic and nanomechanical devices, where grain boundaries and interfacial disorder strongly limit thermal dissipation. Although classical interatomic potentials enable large-scale simulations, their limited transferability can lead to inaccuracies in vibrational properties and interfacial phonon scattering. In this work, we develop a machine learning-based framework for modeling thermal transport in bulk and nanocrystalline silicon by combining Gaussian approximation potential and multi-atomic cluster expansion models with lattice-dynamical calculations and molecular dynamics. Harmonic and anharmonic force constants derived from machine-learning interatomic potentials (MLIPs) are used within a unified Phonopy/Phono3py workflow to compute phonon dispersions, lifetimes, and lattice thermal conductivity, providing an internally consistent description of vibrational properties. In nanocrystalline silicon, non-equilibrium molecular dynamics simulations directly quantify the thermal boundary resistance associated with grain boundaries and reveal its sensitivity to interfacial roughness and the underlying interatomic description. Compared with the Stillinger-Weber and Tersoff potentials, the MLIPs provide a quantitatively accurate and internally consistent description of bulk and interfacial phonon transport, enabling better predictive modeling of nanoscale thermal transport in low-dimensional materials.

cond-mat.mtrl-sci↗

arXiv2025

Extended Multi-Temperature Model for Electron--Phonon Coupling and Ultrafast Thermal Transport in Graphene

Ultrafast thermal transport in low-dimensional materials challenges traditional diffusive models due to reduced scattering, strong electron-phonon coupling, and pronounced non-equilibrium effects. To address these complexities, we extend the macroscopic multi-temperature model by incorporating non-diffusive and non-local phenomena, treating electrons, optical phonons, and acoustic phonons as coupled but thermally distinct subsystems. We benchmark this enhanced framework against the multi-temperature Boltzmann transport equation, enabling detailed resolution of branch-dependent energy relaxation and identifying bottlenecks in thermalization. This approach provides a more accurate and comprehensive description of heat flow in emerging materials, offering novel insights into phonon dynamics and electron-phonon interactions. These theoretical advances pave the way for the improved design and optimization of next-generation nanoelectronic and photothermal devices.

cond-mat.mes-hall↗

arXiv2025

Giant Enhancement of Phonon Electron Coupling in Graphene under Femtosecond Laser Heating at Room Temperature

In recent years, phonon electron carrier dragging has emerged as an innovative approach for modulating energy transfer in low dimensional systems. In this Letter, we explore the fundamental mechanisms of electron-phonon coupling and the role of thermal lag behavior in ultrafast heat transport. We present a theoretical investigation of non-equilibrium thermal dynamics in graphene under femtosecond laser excitation, emphasizing the role of phonon branch-resolved electron phonon coupling. This framework provides new insight into ultrafast energy transfer processes at femtosecond timescales and illustrates key deviations from the predictions of the classical two temperature model (TTM), particularly in spatially localized heat transport. Our results show that a 190 fs laser pulse induces a strong non-equilibrium state, followed by momentum redistribution among the excited carriers. This is then followed by effective cooling of the carrier distribution on a 450 fs timescale through phonon emission.

cond-mat.mes-hall↗

arXiv2025

Spatially Mapping Phonon Drag in Ultrascaled 5-nm Silicon Nanowire Field-Effect Transistor Based on a Quantum Hydrodynamic Formalism

The growing demand for better performance and lower thermal energy dissipation in nanoelectronic devices is the major driving force of the semiconductor industry's quest for future generations of nanotransistors. Over the past 15 years, the miniaturization of silicon-based nanoelectronics predicted by Moore's law has driven an aggressive scaling down of transistor structures, including materials, design, and geometries. In this regard, the electronic device community has expanded its focus to ultrascaled transistors targeting the 7 nm technology node and beyond. However, these emerging nanodevices also present thermal challenges that can limit carrier transport as a result of strong electron-phonon coupling. In this work, we investigate the physical origin of self-heating effects in an ultrascaled 5 nm silicon nanowire field-effect transistor. Based on a quantum hydrodynamic approach, we also provide an explanation of the phonon drag contribution to thermal conductivity. We report the impact of the phonon drag effect on the electrical and thermal performance of 5 nm gate-all-around silicon nanowire field-effect transistors. Our findings provide new insight into the origin of self-heating as a result of mutual electron-phonon coupling. Furthermore, we demonstrate that the phonon drag effect significantly reduces thermal conductivity by nearly 50% under high-bias conditions.

cond-mat.mes-hall↗

arXiv2025

Non-equilibrium transport and phonon branch-resolved size effects based on a multi-temperature kinetic model

Non-equilibrium transport and phonon branch-resolved size effects in single-layer graphene materials are studied under a multi-temperature kinetic model, which is developed for capturing the branch-dependent electron-phonon coupling. Compared with typical macroscopic multi-temperature models, the assumption of diffusive phonon transport is abandoned in this model and replaced by the free migration and scattering of particles. The phonon branch- and size-dependent effective thermal conductivity is predicted in nanosized graphene as well as the temperature slips near the boundaries. Compared with other phonon branches, the ZA branch contributes the most to thermal conduction regardless of system sizes. Furthermore, in nanosized homogeneous graphene with a hotspot at the center, the branch-dependent thermal conductivity increases from the inside to the outside even if the system size is fixed. The thermal conductivity of ZA branch is even higher than the lattice thermal conductivity when the system size is hundreds of nanometers.

cond-mat.mes-hall↗