About coupled dipole methods, the role of vacuum fluctuations in heat flux fluctuations, and radiative force fluctuations for arbitrary objects and environments out of equilibrium

• Applicant: Dr. Florian Herz
• Subject Area: Theoretical Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 519479175

My research project belongs to the subject of physics and is concerned about the transport of thermal radiation on scales below the wavelength of the corresponding light. On these length scales, objects can transfer heat radiation beyond the limit postulated by Stefan-Boltzmann law depending on the object’s materials. During my PhD studies, I have already worked on theoretical models to simulate experiments in which one wants to gain information about near-field properties of different materials and configurations. For this, I used a many-body dipole approach to approximate macroscopic objects geometrically. In my research project, I want to improve this model by also covering anisotropic materials, i.e. whose material properties depend on the propagation direction of light. This is, for instance, interesting for magneto-optical materials with which one can influence heat propagation on purpose. Additionally, I want to bring my model closer to experiments by implementing temperature profiles for the materials and surface roughness. Another key point of my research project is to model the dynamical behaviour of such systems. This corresponds to a "switching-on process" when particles transfer heat to another one for the first time until the heat flow reaches equilibrium. For this, one can describe these particles as harmonic oscillators coupled to heat baths. Finally, I want to investigate the impact of vacuum fluctuations on the fluctuations of the heat transfer between two objects. During my PhD studies, I encountered these in addition to the thermal fluctuations. Because of their divergent properties, it was rather difficult to interpret them. Subsequently, I want to generalize the already existing relations of the fluctuations of radiative forces to arbitrary geometries and materials not being in a global equilibrium state. I want to work on this research project at the Intitut d’Optique in Palaiseau, France. This institute belongs to Paris-Saclay University having an excellent reputation in mathematics and physics, especially in my subject of research. My future mentor Dr. Philippe Ben-Abdallah belongs to the most outstanding scientists on this subject. Hence, I hope to gain a great amount of experience and knowledge from my two years of stay there for my further academic career.

• DFG Programme: WBP Fellowship
• International Connection: France
• Host: Philippe Ben-Abdallah, Ph.D.