Hybrid k • p tight-binding model for subbands and infrared intersubband optics in few-layer films of transition-metal dichalcogenides: MoS_2, MoSe_2, WS_2, and WSe_2

摘要

We present a density functional theory parametrized hybrid k • p tight-binding model for electronic properties of atomically thin films of transition-metal dichalcogenides, 2H-MX_2 (M = Mo. W; X = S. Se). We use this model to analyze intersubband transitions in p- and n-doped 2H-MX_2 tilms and predict the line shapes of the intersubband excitations, determined by the subband-dependent two-dimensional electron and hole masses, as well as excitation lifetimes due to emission and absorption of optical phonons. We find that the intersubband spectra of atomically thin films of the 2H-MX_2 family with thicknesses of N = 2 to 7 layers densely cover the infrared spectral range of wavelengths between 2 and 30 μm. The detailed analysis presented in this paper shows that for thin n-doped films, the electronic dispersion and spin-valley degeneracy of the lowest-energy subbands oscillate between odd and even number of layers, which may also offer interesting opportunities for quantum Hall effect studies in these systems.