Excitonic structure of the optical conductivity in MoS2 monolayers

Abstract

We investigate the excitonic spectrum of MoS2 monolayers and calculate its optical absorption properties over a wide range of energies. Our approach takes into account the anomalous screening in two dimensions and the presence of a substrate, both cast by a suitable effective Keldysh potential. We solve the Bethe-Salpeter equation using as a basis a Slater-Koster tight-binding model parameterized to fit the ab initio MoS2 band structure calculations. The resulting optical conductivity is in good quantitative agreement with existing measurements up to ultraviolet energies. We establish that the electronic contributions to the C excitons arise not from states at the Γ point, but from a set of k-points over extended portions of the Brillouin zone. Our results reinforce the advantages of approaches based on effective models to expeditiously explore the properties and tunability of excitons in TMD systems.

Layer‐Dependent Dielectric Function of Wafer‐Scale 2D MoS2

“…Specifically, it may be associated with the six nearly degenerate exciton states made from transitions between V 1 and the first three lowest conduction bands (C 1–3 ) . The broad CP C can be understood from the fact that the electronic states between the K and Γ points contain mostly contributions from the nonlocalized p orbitals character of the sulfur atoms . The electron transitions from V 1 to C 1–3 around Γ point in the BZ give rise to the CP D. It should be noted that the valance and conduction bands involved in the electron transitions of the CPs C and D are of the same type except that the transition positions are different.…”

Gauge invariance of excitonic linear and nonlinear optical response

“…For instance, using the CVG interaction, as in Refs. [31] and [43], results in an incorrect excitonic optical response regardless of the basis completeness, as will be demonstrated in Sec. II C. In addition to the gauge freedom, it is well known that the optical response can be computed in two ways: direct evaluation of the current density and via the time derivative of the polarization density [19,40].…”

Combined tensor network/cluster expansion method using logic gates: Illustrated for (bi)excitons by a single-layer MoS2 model system

“…, the TN constructing this coherence from S(k L 1 k L 2 k L 3 k L 4 |) is given in the Supplemental material. We obtain the bound, bright A exciton at1 1.769 eV compared to a band gap of 2.124 eV at the K-point, reproducing [54], whose band structure [53,54] is used in the model system, here. As an example from the exciton states, Fig.…”

“…The electronic bandstructure enters the Hamiltonian through H 0 = kλ ε λ k a † kλ a kλ , here k is the quasi momentum in BZ, and λ describes band and spin. ε λ k is the bandstructure of the material, for this paper the tight binding bandstructure for MoS 2 from [53,54] is used. Depending on the band λ = c σ , v σ distinguishing conduction c and valence band v, a † kλ with spin σ =↑, ↓ , a kλ are the creation and annihilation operator of an electron (conduction band) or hole (valence band):…”