Official websites use. Share sensitive information only on official, secure websites. Optical spectroscopy of ultimately thin materials has significantly enhanced our understanding of collective excitations in low-dimensional semiconductors. This is particularly reflected by the rich physics of excitons in atomically thin crystals which uniquely arises from the interplay of strong Coulomb correlation, spin-orbit coupling SOC , and lattice geometry. Here we extend the field by reporting the observation of room temperature excitons in a material of non-trivial global topology.
These experimental findings are corroborated, concerning both the character of the excitonic resonances as well as their energy scale, by ab-initio GW and Bethe-Salpeter equation calculations, confirming strong Coulomb interaction effects in these optical excitations. Our observations provide evidence of excitons in a 2D QSH insulator at room temperature, with excitonic and topological physics deriving from the very same electronic structure. Here, the authors report the observation of room temperature excitons in a single layer of bismuth atoms epitaxially grown on a SiC substrate - a material of non-trivial global topology - with excitonic and topological physics deriving from the very same electronic structure.
Optical spectroscopy conducted on atomically thin sheets of transition metal dichalcogenides TMDCs has opened a broad spectrum of fundamental research, and significantly enhanced our understanding of the physics of elementary excitations in low-dimensional semiconductors 1 , 2.
Indeed, the dramatic increase of Coulomb correlations in two-dimensional structures has revealed the emergence of a vast variety of many-body states, including non-hydrogenic Rydberg series of excitons 3 , stable charged- 4 , 5 , and multi-excitonic complexes 6 , 7.
Our observation of excitons in a large-gap QSH insulator at room temperature opens up a new exciting avenue of combining excitonic physics and topological electronic properties. Here a first central step was recognizing that the optical selection rules are governed by the winding number of the low-energy gapped Dirac bandstructure, which like the Berry curvature, is a "local" topological quantity in k -space 8 — This local physics is indeed determined by the Berry curvature flux through the small k -space spanned by the relative motion of the e — h pair in the excitonic wavefunction This appears, e.
