Exciton-phonon interaction in the strong-coupling regime in hexagonal boron nitride

Phuong Vuong (1) , Guillaume Cassabois (1) , Pierre Valvin (1) , Song Liu (2) , Jim Edgar (2) , Bernard Gil (1)

1 L2C - Laboratoire Charles Coulomb
2 KSU

The temperature-dependent optical response of excitons in semiconductors is controlled by the exciton-phonon interaction. When the exciton-lattice coupling is weak, the excitonic line has a Lorentzian profile resulting from motional narrowing, with a width increasing linearly with the lattice temperature T . In contrast, when the exciton-lattice coupling is strong, the line shape is Gaussian with a width increasing sublinearly with the lattice temperature, proportional to sqrt(T) . While the former case is commonly reported in the literature, here the latter is reported for hexagonal boron nitride. Thus the theoretical predictions of Toyozawa [Prog. Theor. Phys. 20, 53 (1958)] are supported by demonstrating that the exciton-phonon interaction is in the strong-coupling regime in this van der Waals crystal.

Domaines: Autre [cond-mat.other]

Phuong Vuong, Guillaume Cassabois, Pierre Valvin, Song Liu, Jim Edgar, et al.. Exciton-phonon interaction in the strong-coupling regime in hexagonal boron nitride. Physical Review B, 2017, 95, pp.201202(R). ⟨10.1103/PhysRevB.95.201202⟩. ⟨hal-01528598⟩