First-principles many-body theory for charged and neutral excitations: Trion fine structure splitting in transition metal dichalcogenides

Band nesting and exciton spectrum in monolayer MoS2

“…Therefore, for low CB spin splitting as obtained in ab initio calculations, ∆ CB SOC = 4 meV in MoS 2 18 , even though spin ordering of lowest energy single particle electron-hole transitions renders them still bright, the lowest excitonic state is dark, as illustrated in Fig. 7 left and suggested also by GW-BSE calculations 103,104 and some experiments 105 . We now turn to discuss the role of intra-valley exchange interaction.…”

“…Greens function based DFT+GW+Bethe-Salpeter approach 103 suggests taking unscreened value of exchange interaction. This issue needs further investigation 104,106 . However, irrespective of the approach, we conclude that the dark A exciton is the lowest energy exciton state, ∼ 3 − 10 meV below the bright exciton in MoS 2 .…”

Trion induced photoluminescence of a doped MoS2 monolayer

“…[41][42][43][44] Due to rapid advances of the computational methods and computing power, direct diagonalization of the corresponding three-particle Hamiltonian is now possible. [45][46][47][48][49][50][51][52][53] However, until now, the main attention has been focused on trions with zero center-of-mass momentum. Certain progress in the studies of non-zero momentum neutral (two-particle) excitons was achieved for undoped systems.…”

“…Following the conventional classification, one distinguishes two types of trion states-with |s c 1 z + s c 2 z | = 1, 0. 38,51,52,54,63 One can also define the intra-and inter-valley states as those with |τc 1 + τc 2 | = 2 and 0, respectively. 51,52 The fermionic trion states can also be classified by the product Szτ of the total spin Sz and the total valley τ = τc 1 + τc 2 − τv quantum numbers.…”

Excitonic theory of doping-dependent optical response in atomically thin semiconductors

“…Ab initio calculations of the trion binding energy are commonly available for monolayer TMDCs [30][31][32][33][34]. In contrast, a complete fully microscopic theory of the doping-dependent absorption spectra has not been provided so far: Available theoretical studies are based on phenomenological approaches which start from approximate variational exciton and trion states [35][36][37][38][39][40][41][42][43].…”