Temperature dependent moiré trapping of interlayer excitons in MoSe2-WSe2 heterostructures

Mahdikhanysarvejahany, Fateme; Shanks, Daniel N.; Muccianti, Christine; Badada, Bekele; Idi, Ithwun; Alfrey, Adam; Raglow, Sean; Köehler, Michael; Mandrus, David; Taniguchi, Takashi; Watanabe, Kenji; Monti, Oliver L. A.; Yu, Hongyi; LeRoy, Brian J.; Schaibley, John

doi:10.1038/s41699-021-00248-7

Cited by 25 publications

(28 citation statements)

References 33 publications

(55 reference statements)

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“…Figure 1c shows co- and cross-circularly polarized PL when exciting the hBN-separated region with a 1.72 eV laser and detecting from both regions. Surprisingly, while the DC region shows the cross-circularly polarized PL, consistent with previous studies on R-type structures 5 , 7 , 15 , the hBN-separated region shows mostly co-circularly polarized PL (see Supplementary Fig. 3 for similar data from another sample).…”

Section: Resultssupporting

confidence: 90%

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Localized interlayer excitons in MoSe2–WSe2 heterostructures without a moiré potential

Mahdikhanysarvejahany

Shanks

Klein

et al. 2022

Nat Commun

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Interlayer excitons (IXs) in MoSe2–WSe2 heterobilayers have generated interest as highly tunable light emitters in transition metal dichalcogenide (TMD) heterostructures. Previous reports of spectrally narrow (<1 meV) photoluminescence (PL) emission lines at low temperature have been attributed to IXs localized by the moiré potential between the TMD layers. We show that spectrally narrow IX PL lines are present even when the moiré potential is suppressed by inserting a bilayer hexagonal boron nitride (hBN) spacer between the TMD layers. We compare the doping, electric field, magnetic field, and temperature dependence of IXs in a directly contacted MoSe2–WSe2 region to those in a region separated by bilayer hBN. The doping, electric field, and temperature dependence of the narrow IX lines are similar for both regions, but their excitonic g-factors have opposite signs, indicating that the origin of narrow IX PL is not the moiré potential.

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Section: Resultssupporting

confidence: 90%

“…1b). In the DC region of the device the IX photon energy is centered around 1.34 eV, consistent with R-type (near 0°twist) MoSe 2 -WSe 2 heterostructures 15 . The hBN separated region shows higher energy PL centered around 1.42 eV.…”

Section: Resultssupporting

confidence: 67%

Localized interlayer excitons in MoSe2–WSe2 heterostructures without a moiré potential

Mahdikhanysarvejahany

Shanks

Klein

et al. 2022

Nat Commun

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“…First, the trapped IX has a lower energy, so the free IX can relax to the trapped IX before its decay. Second, the non-radiative decay rate could be suppressed for the trapped IX due to the suppressing of IX diffusion 21 . Additionally, we note that when a field is applied in the opposite direction, such that the IX energy is decreased, there is no additional signal from the removed graphene area (Extended Data Fig.…”

Section: Main Textmentioning

confidence: 99%

Nanoscale Trapping of Interlayer Excitons in a 2D Semiconductor Heterostructure

Shanks

Mahdikhanysarvejahany

Muccianti

et al. 2021

Nano Lett.

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For quantum technologies based on single excitons and spins, the deterministic placement and control of a single exciton is a longstanding goal. MoSe 2 -WSe 2 heterostructures host spatially indirect interlayer excitons (IXs) that exhibit highly tunable energies and unique spin-valley physics, making them promising candidates for quantum information processing. Previous IX trapping approaches involving moireś uperlattices and nanopillars do not meet the quantum technology requirements of deterministic placement and energy tunability. Here, we use a nanopatterned graphene gate to create a sharply varying electric field in close proximity to a MoSe 2 -WSe 2 heterostructure. The dipole interaction between the IX and the electric field creates an ∼20 nm trap. The trapped IXs show the predicted electric-field-dependent energy, saturation at low excitation power, and increased lifetime, all signatures of strong spatial confinement. The demonstrated architecture is a crucial step toward the deterministic trapping of single IXs, which has broad applications to scalable quantum technologies.

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“…Although there have been several theoretical reports on the impact of strain on the energy level [70][71][72][73], not much is known about the microscopic impact of strain on the spin-valley physics, particularly on the spin-mixing and g-factors. Revealing the isolate impact of strain on the spin-valley physics provides fundamental insight on possible fluctuations on the spin and valley dependent properties of TMDC monolayers as well as TMDC-based van der Waals heterostructures [4,69,[74][75][76][77][78][79][80][81][82][83]. This fundamental understanding is also relevant to the theoretical modelling of van der Waals heterostructures within first-principles, in which strain is often needed to effectively create commensurate supercells.…”

Section: Introductionmentioning

confidence: 98%

First-principles insights into the spin-valley physics of strained transition metal dichalcogenides monolayers

et al. 2022

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Transition metal dichalcogenides (TMDCs) are ideal candidates to explore the manifestation of spin-valley physics under external stimuli. In this study, we investigate the influence of strain on the spin and orbital angular momenta, effective g-factors, and Berry curvatures of several monolayer TMDCs (Mo and W based) using a full ab initio approach. At the K-valleys, we find a surprising decrease of the conduction band spin expectation value for compressive strain, consequently increasing the dipole strength of the dark exciton by more than one order of magnitude (for ∼ 1 % – 2 % strain variation). We also predict the behavior of direct excitons g-factors under strain: tensile (compressive) strain increases (decreases) the absolute value of g-factors. Strain variations of ∼1% modify the bright (A and B) excitons g-factors by ∼0.3 (0.2) for W (Mo) based compounds and the dark exciton g-factors by ∼0.5 (0.3) for W (Mo) compounds. Our predictions could be directly visualized in magneto-optical experiments in strained samples at low temperature. Additionally, our calculations strongly suggest that strain effects are one of the possible causes of g-factor fluctuations observed experimentally. By comparing the different TMDC compounds, we reveal the role of spin–orbit coupling (SOC): the stronger the SOC, the more sensitive are the spin-valley features under applied strain. Consequently, monolayer WSe2 is a formidable candidate to explore the role of strain on the spin-valley physics. We complete our analysis by considering the side valleys, Γ and Q points, and by investigating the influence of strain in the Berry curvature. In the broader context of valley- and strain-tronics, our study provides fundamental microscopic insights into the role of strain in the spin-valley physics of TMDCs, which are relevant to interpret experimental data in monolayer TMDCs as well as TMDC-based van der Waals heterostructures.

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Temperature dependent moiré trapping of interlayer excitons in MoSe2-WSe2 heterostructures

Cited by 25 publications

References 33 publications

Localized interlayer excitons in MoSe2–WSe2 heterostructures without a moiré potential

Localized interlayer excitons in MoSe2–WSe2 heterostructures without a moiré potential

Nanoscale Trapping of Interlayer Excitons in a 2D Semiconductor Heterostructure

First-principles insights into the spin-valley physics of strained transition metal dichalcogenides monolayers

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