Non-diffusive heat conduction mechanisms from crystalline to amorphous materials

In recent years, a substantial body of research has demonstrated that thermal diffusion —the macroscopic transport mechanism governing heat dissipation in solids — does not explain the evolution of thermal energy at the nanoscale. The breakdown of diffusion has an enormous technological impact, since it prevents informed design for thermal management in energy conversion and data processing electronic devices. Fundamental understanding of nanoscale heat transport remains out of reach, and current models beyond diffusion are not universal and display limited applicability.

This project aims to experimentally identify general thermal transport mechanisms emerging at the nanoscale across different materials, from amorphous to crystalline structures. The research approach will combine theoretical and experimental perspectives. First, the candidate will be involved in the design and fabrication of heterogeneous nanoscale structures including metals and semiconductors in both crystalline and amorphous forms. Second, he/she will perform time-resolved thermal conductivity measurements. Finally, he/she will model the experimental data using both diffusive and nondiffusive simulations including hydrodynamic transport effects with a Finite Element solver. The final goal is to identify deviations from macroscopic diffusion in a range of nonequilibrium conditions at different length and time scales. Complementary, the candidate will be involved in the comparison between experiments and molecular dynamics simulations of the atomistic
dynamics.

This project is the core of a self-contained experiment-theory research collaboration. Hence, the candidate is expected to demonstrate a high degree of flexibility and capacities to both perform specialized fabrication and experimental tasks and develop a deep understanding of the theoretical framework and modeling tools. This will require communication skills, capacity to learn, and abilities to work in an interdisciplinary environment, along with a keen interest in material physics and nanoscience and nanotechnology cutting edge problems. Regarding the academic requirements, advanced training in solid state physics, statistical physics and thermodynamics will be positively evaluated. Additionally, previous research experience and other skills such as programming will be considered

This research project is a continuation of a previous collaboration between Aitor and Albert within the Department of Physics of the Universitat Autònoma de Barcelona. The research group includes other UAB professors with experimental and theoretical backgrounds, including Profs. Javier Rodriguez, Juan Camacho, and F. Xavier Alvarez.
Aitor has expertise in fabrication and advanced characterization methods to prove thermal properties of nanomaterials. Albert has expertise on theoretical development of nonequilibrium thermodynamics and hydrodynamic thermal transport models tailored to describe heat transport effects emerging at the nanoscale. These two backgrounds are complementary and synergetic, and enable comprehensive development of the research project, where the design and fabrication of nanodevices is informed by theory, and the development of transport models and new theory is guided by the experiments.

Since 2020, Libertad Abad has been a member of MESSI-IMB-CNM-CSIC, a group that develops micro energy and smart sensing devices to tackle long-term challenges like “Healthier Citizens” and “Net Zero Human Impact.” She has collaborated for over 20 years with Aitor on projects related to thermoelectricity, nanocalorimetry, and nanoscale thermal measurements. The group explores environmental energy harvesting (thermoelectricity) and energy generation/storage using micro fuel cells and biodegradable batteries, along with advanced sensor systems. A key focus is micro integrating energy sources and sensors into autonomous, self-powered platforms by leveraging standard silicon technologies, rapid prototyping, and additive manufacturing.