Excitons, trions, and biexcitons in transition-metal dichalcogenides: Magnetic-field dependence

Donck, M. Van der; Zarenia, M.; Peeters, F. M.

doi:10.1103/physrevb.97.195408

Cited by 65 publications

(44 citation statements)

References 77 publications

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“…Meanwhile the 2s-1s separation is less than 8 times the 3s-2s separation, deviating from the Fig.3b). An independent calculation found 1s exciton to be 0.08 2 ⁄ on a SiO2 substrate 45 . The exciton energies are found to be 1.731 eV (1s), 1.859 eV (2s), and 1.882 eV (3s), in excellent agreement with experimental data.…”

Section: Exciton Physics In Layered Hexagonal Transition Metal Dichalmentioning

confidence: 99%

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe₂

Chen

Goldstein

et al. 2019

Nano Lett.

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We report the experimental observation of radiative recombination from Rydberg excitons in a two-dimensional semiconductor, monolayer WSe2, encapsulated in hexagonal boron nitride.Excitonic emission up to the 4s excited state is directly observed in photoluminescence spectroscopy in an out-of-plane magnetic field up to 31 Tesla. We confirm the progressively larger exciton size for higher energy excited states through diamagnetic shift measurements. This also enables us to estimate the 1s exciton binding energy to be about 170 meV, which is significantly smaller than most previous reports. The Zeeman shift of the 1s to 3s states, from both luminescence and absorption measurements, exhibits a monotonic increase of -factor, reflecting nontrivial magnetic-dipole-moment differences between ground and excited exciton states. This systematic evolution of magnetic dipole moments is theoretically explained from the spreading of the Rydberg states in momentum space.

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Section: Exciton Physics In Layered Hexagonal Transition Metal Dichalmentioning

confidence: 99%

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe₂

Chen

Goldstein

et al. 2019

Nano Lett.

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“…But for the dark exciton/trions, their associated spin triplet will contribute an additional g-factor of -4. This will make their total g-factor about twice of that of bright trions [18,31].…”

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confidence: 99%

Gate Tunable Dark Trions in Monolayer WSe2

et al. 2019

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We report the observation and gate manipulation of intrinsic dark trions in monolayer WSe2. By using ultraclean WSe2 devices encapsulated by boron nitride, we directly resolve the weak photoluminescence of dark trions. The dark trions can be tuned continuously between negative and positive charged trions with electrostatic gating. We also reveal their spin triplet configuration and distinct valley optical emission by their characteristic Zeeman splitting under magnetic field. The dark trions exhibit large binding energy (14 -16 meV). Their lifetime (~1.3 ns) is two orders of magnitude longer than the bright trion lifetime (~10 ps) and can be tuned between 0.4 to 1.3 ns by electrostatic gating. Such robust, optically detectable, and gate tunable dark trions provide a new path to realize electrically controllable trion transport in two-dimensional materials.Monolayer transition metal dichalcogenides (TMDs), such as MoS2 and WSe2, are remarkable two-dimensional (2D) semiconductors with strong Coulomb interactions [1, 2]. Their optical properties are dominated by tightly bound electron-hole pairs (excitons) at two time-reversal valleys (K, K') in the momentum space [3]. The strong spin-orbit coupling splits both the conduction and valence bands into two subbands with opposite spins [Fig. 1] [4-7]. The spin configuration governs an exciton's optical properties. If the electron and hole come from bands with the same electron spin, their recombination can efficiently emit light. These bright excitons have short lifetime (<10 ps) [8], in-plane dipole moment and out-of-plane light emission [Fig. 1] [9]. But if the electron and hole come from bands with opposite electron spins, the spin mismatch strongly suppresses their radiative recombination. They form dark excitons with long lifetime (>100 ps), out-ofplane dipole moment, and in-plane light emission [Fig. 1] [10-18]. Compared to bright excitons, the long-lived dark excitons are much better candidates for the studies of exciton transport and Bose-Einstein condensate [19-21], but their optical inactivity poses a significant challenge for experiment.Monolayer WSe2 is an exceptional material to explore dark excitons. Unlike other semiconductors (e.g. MoSe2) with bright excitons in the lowest energy level, monolayer WSe2 hosts dark excitons well below the bright exciton level [ Fig. 1] [6, 13, 22]. The dark excitons can thus accumulate a sufficiently large population to achieve observable light emission, as reported by prior research [16,[23][24][25][26]. Moreover, as the dark excitons lie at the lowest energy level, they play a crucial role in the carrier dynamics of monolayer WSe2. It is therefore important to understand their diverse properties.Similar to bright excitons/trions, dark excitons can capture an extra charge to form dark trions [ Fig. 1]. The dark trions are fascinating entities for excitonic transport, because their finite net charge, together with their long lifetime, would enable effective control of exciton dynamics by electric field. However, detection an...

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“…The 1L-WSe 2 /GO region displays a lower PL intensity compared with the 1L-WSe 2 region without GO. [35,36] Figure 2e shows the fitted PL spectrum of 1L-WSe 2 /GO and reveals that the spectral weight of the trion contribution is increased and the exciton contribution is reduced compared with 1L-WSe 2 as shown in Figure 2f. The PL peak position of 1L-WSe 2 was shifted to a lower energy when 1L-WSe 2 was deposited on top of GO.…”

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confidence: 94%

Suppressing Ambipolar Characteristics of WSe₂ Field Effect Transistors Using Graphene Oxide

Park

Bang

et al. 2018

Adv Elect Materials

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Monolayer (1L) tungsten diselenide (WSe2) is of interest for next generation ultrathin flexible electronic devices. However, typical WSe2 field effect transistors (FETs) show ambipolar characteristics that are not desirable for complementary field‐effect‐transistors and circuits. Here, significant suppression of the ambipolar characteristics of a 1L‐WSe2 FET is demonstrated by using an electron withdrawing functional group of graphene oxide (GO). The pristine 1L‐WSe2 FET shows n‐type dominant ambipolar characteristics, whereas the GO coated 1L‐WSe2 FET shows unipolar p‐type behavior with a huge decrease (1/106) of current level of the n‐channel. Also, the current level of the p‐channel increases up to ten times that of the pristine 1L‐WSe2 FET. These results are applicable for the realization of flexible nanoscale digital logic devices by using transition metal dichalcogenides.

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Excitons, trions, and biexcitons in transition-metal dichalcogenides: Magnetic-field dependence

Cited by 65 publications

References 77 publications

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe₂

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe₂

Gate Tunable Dark Trions in Monolayer WSe2

Suppressing Ambipolar Characteristics of WSe₂ Field Effect Transistors Using Graphene Oxide

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Excitons, trions, and biexcitons in transition-metal dichalcogenides: Magnetic-field dependence

Cited by 65 publications

References 77 publications

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe2

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe2

Gate Tunable Dark Trions in Monolayer WSe2

Suppressing Ambipolar Characteristics of WSe2 Field Effect Transistors Using Graphene Oxide

Contact Info

Product

Resources

About

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe₂

Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe₂

Suppressing Ambipolar Characteristics of WSe₂ Field Effect Transistors Using Graphene Oxide