From 3D to 1D systems: emergent phenomena in phononics and thermal transport
In many nanostructured materials, while strong covalent bonding provides the stability of the sub-nanometric elementary units, the whole assembly is held together by weak van der Waals interactions. The individual building blocks hence maintain most of their intrinsic characteristics also when arranged together to form a crystalline solid. In principle, novel material properties can be thus tailored by controlling those of the elementary units. This bottom-up strategy in the synthesis of new materials has been intensively followed since the '80s, when small atomic aggregates, nanoclusters, fullerenes, nanotubes, etc. started to attract enormous attention[1-2]. In this context, the interest in low-dimensional materials is self-evident. On the one hand, the physics of many-body systems, limited in 2D or 1D presents a plethora of unusual fascinating properties; on the other hand, the reduction of dimensionality allows us to perform gedanken experiments for testing and better understanding physical models. In this talk I will present different examples of emergent phenomena in multi-layered, 2D and 1D systems [3-5]. [1] M. S. Dresselhaus, G. Dresselhaus, and P. C. Eklund, Science of Fullerenes and Carbon Nanotubes: Their Properties and Applications (Academic, San Diego, 1996). [2] P. Moriarty, Rep. Prog. Phys. 64, 297 (2001). [3] C. Elias et al. “ Flat bands and giant light-matter interaction in hexagonal boron nitride” PRL (2021). [4] T. Kang et al. " Ultrafast nonlinear phonon response of few-layer hexagonal boron nitride ” PRB-L (2021). [5] C. Melis et al. “Room Temperature Second Sound in Cumulene” Phys. Chem. Chem. Phys. 23, 15275-15281 (2021)