Published: 15 August 2019, 11:44
Place: Zentrum für Angewandte Forschung (ZAF), Philosophenweg 7, 07743 Jena
Time: 16 c.t., 18.09.2019 (Wednesday)
Abstract: Atomic monolayers of transition metal dichalcogenides (TMDs) such as MoS2 and WSe2 have remarkable properties for fundamental research and potential applications : They are semiconductors with a direct gap in the visible to near infrared region of the optical spectrum. The interaction of TMD monolayers with light is governed by excitons , electron-hole pairs bound by Coulomb attraction, with binding energies of several hundred meV and therefore still dominant at room temperature. Light-matter interaction is enhanced at specific exciton resonances with 20 % of the light absorbed per monolayer and modulation of several orders of magnitude of second harmonic generation efficiency, for example. Recent progress in fabrication allows approaching lifetime broadened optical transitions and in this regime TMD monolayers can in principle be tuned to 100 % reflectivity i.e. to be perfect mirrors. In addition, chiral optical selection rules allow for optical manipulation of the spin and valley index of electrons with polarized lasers, opening research opportunities in spintronics and valleytronics.
Here we review our current understanding of the optical and polarization properties of TMD monolayers and heterostructures and how they can be coupled to photonic structures or magnetic substrates using simple “Scotch tape” exfoliation techniques for assembly , to further explore their properties.
 “Excitons in atomically thin transition metal dichalcogenides," Wang, A. Chernikov, M. M. Glazov, T. F. Heinz, X. Marie, T. Amandd, B. Urbaszek, Reviews of Modern Physics 90 (2), 021001 (2018) and arXiv : 1707.05863.
 “Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition, ” Shree, A. George, T. Lehnert, Ch. Neumann, M. Benelajla, C. Robert, X. Marie, K. Watanabe, T. Taniguchi, U. Kaiser, B. Urbaszek, A. Turchanin arXiv:1907.03342 (submitted).