Theory of neutral and charged excitons in monolayer transition metal dichalcogenides

Berkelbach, Timothy C.; Hybertsen, Mark S.; Reichman, David R.

doi:10.1103/physrevb.88.045318

Cited by 862 publications

(1,137 citation statements)

References 44 publications

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“…Substituting χ 2D from Ref. 50, we conclude that for TMDC ρ 0 is estimated as 38Å for WS 2 , 41Å for MoS 2 , 45Å for WSe 2 , 52Å for MoSe 2 . The binding energy for the dipolar exciton was estimated for two MoS 2 layers separated by N hBN insulating layers from N = 1 up to N = 6 [53].…”

Section: Two-body Problem For Dirac Particles With a Gapmentioning

confidence: 80%

“…The properties of direct excitons in mono-and few-layer TMDCs on a SiO 2 substrate were experimentally and theoretically investigated, identifying and characterizing not only the ground-state exciton but the full sequence of excited (Rydberg) exciton states [46]. The exciton binding energy for monolayer, few-layer and bulk TMDCs and optical gaps were evaluated using the tight-binding approximation [47], by solving the BSE [48,49], applying an effective mass model, density functional theory and subsequent random phase approximation calculations [50], and by a generalized time-dependent density-matrix functional theory approach [51]. Significant spin-orbit splitting in the valence band leads to the formation of two distinct types of excitons in TMDC layers, labeled A and B [50].…”

Section: Introductionmentioning

confidence: 99%

“…The exciton binding energy for monolayer, few-layer and bulk TMDCs and optical gaps were evaluated using the tight-binding approximation [47], by solving the BSE [48,49], applying an effective mass model, density functional theory and subsequent random phase approximation calculations [50], and by a generalized time-dependent density-matrix functional theory approach [51]. Significant spin-orbit splitting in the valence band leads to the formation of two distinct types of excitons in TMDC layers, labeled A and B [50]. colorred Type A excitons are formed by spin-up electrons from conduction and spin-down holes from valence bands.…”

Section: Introductionmentioning

confidence: 99%

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High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

Berman

Kezerashvili

2016

Phys. Rev. B

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The high-temperature superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers is predicted. We study Bose-Einstein condensation in the two-component system of dipolar A and B excitons. The effective mass, energy spectrum of the collective excitations, the sound velocity and critical temperature are obtained for different TMDC materials. It is shown that in the Bogolubov approximation the sound velocity in the two-component dilute exciton Bose gas is always larger than in any one-component. The difference between the sound velocities for two-component and one-component dilute gases is caused by the fact that the sound velocity for a two-component system depends on the reduced mass of A and B excitons, which is always smaller than the individual mass of A or B exciton. Due to this fact, the critical temperature Tc for superfluidity for the twocomponent exciton system in a TMDC bilayer is about one order of magnitude higher than Tc in any one-component exciton system. We propose to observe the superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers, which causes two opposite superconducting currents in each TMDC layer.

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Section: Two-body Problem For Dirac Particles With a Gapmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

Berman

Kezerashvili

2016

Phys. Rev. B

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“…The exciton binding energies in 2D chalcogenides are almost an order of magnitude larger compared to other bulk semiconductors [1][2][3][4][5] . The strong Coulomb interactions and small exciton radii in 2D-TMDs result in large optical oscillator strengths 3,7,8 and short radiative lifetimes 10 .…”

Section: Introductionmentioning

confidence: 93%

Fast exciton annihilation by capture of electrons or holes by defects via Auger scattering in monolayer metal dichalcogenides

Wang¹,

Strait²,

Zhang³

et al. 2015

Phys. Rev. B

114

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The strong Coulomb interactions and the small exciton radii in two-dimensional metal dichalcogenides can result in very fast capture of electrons and holes of excitons by mid-gap defects from Auger processes. In the Auger processes considered here, an exciton is annihilated at a defect site with the capture of the electron (or the hole) by the defect and the hole (or the electron) is scattered to a high energy. In the case of excitons, the probability of finding an electron and a hole near each other is enhanced many folds compared to the case of free uncorrelated electrons and holes. Consequently, the rate of carrier capture by defects from Auger scattering for excitons in metal dichalcogenides can be 100-1000 times larger than for uncorrelated electrons and holes for carrier densities in the 10 11 -10 12 cm −2 range. We calculate the capture times of electrons and holes by defects and show that the capture times can be in the sub-picosecond to a few picoseconds range. The capture rates exhibit linear as well as quadratic dependence on the exciton density. These fast time scales agree well with the recent experimental observations and point to the importance of controlling defects in metal dichalcogenides for optoelectronic applications.

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“…Here, we have introduced the excitonic part of the Coulomb interaction V exc (q, k), which is treated within the thin-film formalism for 2D systems. 8,9,14,48,49 The latter also contains the dielectric background screening ε = ε ε + BG 2 cover substrate of the underlying substrate/cover layer. Figure 5a shows the calculated binding energies of 1s and 2p states of intravalley K−K excitons (parabolae around Q = 0) as well as momentum-forbidden dark K-Λ excitons (parabolae around Q = Λ) as a function of the center-of-mass momentum Q.…”

mentioning

confidence: 99%

Dielectric Engineering of Electronic Correlations in a van der Waals Heterostructure

et al. 2018

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Heterostructures of van der Waals bonded layered materials offer unique means to tailor dielectric screening with atomic-layer precision, opening a fertile field of fundamental research. The optical analyses used so far have relied on interband spectroscopy. Here we demonstrate how a capping layer of hexagonal boron nitride (hBN) renormalizes the internal structure of excitons in a WSe 2 monolayer using intraband transitions. Ultrabroadband terahertz probes sensitively map out the full complex-valued mid-infrared conductivity of the heterostructure after optical injection of 1s A excitons. This approach allows us to trace the energies and line widths of the atom-like 1s−2p transition of optically bright and dark excitons as well as the densities of these quasiparticles. The excitonic resonance red shifts and narrows in the WSe 2 /hBN heterostructure compared to the bare monolayer. Furthermore, the ultrafast temporal evolution of the mid-infrared response function evidences the formation of optically dark excitons from an initial bright population. Our results provide key insight into the effect of nonlocal screening on electron−hole correlations and open new possibilities of dielectric engineering of van der Waals heterostructures.

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Theory of neutral and charged excitons in monolayer transition metal dichalcogenides

Cited by 862 publications

References 44 publications

High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

Fast exciton annihilation by capture of electrons or holes by defects via Auger scattering in monolayer metal dichalcogenides

Dielectric Engineering of Electronic Correlations in a van der Waals Heterostructure

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