DEPARTMENT OF
PHYSICAL CHEMISTRY
Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
Department Online Seminar
Chair: Shuo Dong

Tuesday, February 23, 2021, 4:00 pm
Seminar Link
Dr. Xin Lu
Tulane University, New Orleans, USA
Excitonic Properties of Localized Emitters from Monolayer WSe2 an WSe2/MoSe2 Heterobilayer
Since the discovery of single photon emitters (SPEs) from monolayer WSe2 in 2015, the two-dimensional layered materials, including transition metal dichalcogenides (TMDCs) and hexagonal boron nitride (h-BN), has emerged to be a new playground for exploring quantum emitters and novel spin-photon interface1. A SPE in TMDC is believed to arise from trapping of an exciton by defects, localized strain or moirépotential which occurs in heterobilayer or twisted homobilayer.
In this talk, I will focus on discussing the excitonic properties of these localized emitters from atomically thin TMDC-based structure. I will start by presenting that a localized exciton in monolayer WSe2 can carry a net charge and a resident spin. Subsequently, I will show our experimental demonstration of optical initialization from the singly, positively charged localized exciton2. Next, I will present our experimental result obtained from a WSe2/MoSe2 heterobilayer. We observed that the localized exciton displays a single permanent dipole, which enables energy tunability by the application of out-of-plane electric field. In addition, the repulsive dipole-dipole interaction causes the second excitation to be blue-shifted, which is distinct from the conventional “biexciton” 3,4.
1. M. Atatüre et al. Material platforms for spin-based photonic quantum technologies. Nature Reviews Materials 3, 38-51 (2018).
2. X. Lu, X. Chen, S. Dubey et al. Optical initialization of a single spin-valley in charged WSe2 quantum dots. Nature Nanotechnology 14, 426-431 (2019).
3. W. Li, X. Lu et al. Dipolar interactions between field-tuneable, localized emitters in van der Waals heterostructures. Nature Materials 19, 624-629 (2020).
4. M. Kremser et al. Discrete interactions between a few interlayer excitons trapped at a MoSe2–WSe2 heterointerface. npj 2D Materials and Applications 4, 8 (2020).
5. X. Chen, X. Lu, S. Dubey et al. Entanglement of single-photons and chiral phonons in atomically thin WSe2. Nature Physics 15, 221-227 (2019).

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