Atomically inspiredk·papproach and valley Zeeman effect in transition metal dichalcogenide monolayers

Abstract

We developed a six-band k · p model that describes the electronic states of monolayer transition metal dichalcogenides (TMDCs) in K-valleys. The set of parameters for the k · p model is uniquely determined by decomposing tight-binding (TB) models in the vicinity of K ± -points. First, we used TB models existing in literature to derive systematic parametrizations for different materials, including MoS2, WS2, MoSe2 and WSe2. Then, by using the derived six-band k · p Hamiltonian we calculated effective masses, Landau levels, and the effective exciton g-factor g X 0 in different TMDCs. We showed that TB parameterizations existing in literature result in small absolute values of g X 0 , which are far from the experimentally measured g X 0 ≈ −4. To further investigate this issue we derived two additional sets of k · p parameters by developing our own TB parameterizations based on simultaneous fitting of ab-initio calculated, within the density functional (DFT) and GW approaches, energy dispersion and the value of g X 0 . We showed that the change in TB parameters, which only slightly affects the dispersion of higher conduction and deep valence bands, may result in a significant increase of |g X 0 |, yielding close-to-experiment values of g X 0 . Such a high parameter sensitivity of g X 0 opens a way to further improvement of DFT and TB models.

Momentum-Dark Intervalley Exciton in Monolayer Tungsten Diselenide Brightened via Chiral Phonon

“…The PL peaks in the magneto-PL spectra of the (σσ -) ( Fig. 4a) configuration exhibits a linear blue shift due to the valley Zeeman effects, 20,[44][45][46][47][48][49][50][51][52][53] and the size of the shift in a fixed B field is determined by the g-factor. It is evident from Fig.…”

Direct Observation of Gate-Tunable Dark Trions in Monolayer WSe2

“…1d). As a result, in a non-interacting picture in which the Zeeman splitting is calculated through the individual shift of CBM and VBM associated with the recombination electron-hole pair 29,47 , the magneto-PL spectra of X D + and X D − will share the same Zeeman splitting as the charge-neutral X D . Therefore, we assign the emerging "cross" patterns in the hole-doped and electron-doped WSe2 ( Fig.…”

Hyperfine interaction in atomically thin transition metal dichalcogenides

“…The hyperfine interaction of charge carriers with the host lattice nuclei is a short range interaction [28,65], so it can be conveniently studied within the tight binding approximation. For the sake of simplicity, we limit ourselves with d-orbitals at the metal atoms (thus neglecting s-orbitals [66]) and p-orbitals at the chalcogen atoms [6,55]. In this basis the orbital part of the wavefunction is even with respect to the reflection σ h (z → −z).…”