Regensburg 2022 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 6: 2D Materials 1 (joint session HL/CPP/DS)
HL 6.8: Talk
Monday, September 5, 2022, 12:00–12:15, H36
Millikelvin Spectroscopy on Degenerate Exciton Ensembles in van der Waals Bilayers — •Nihit Saigal1, Torsten Stiehm1, Hendrik Lambers1, Florian Sigger2, Lukas Sigl2, Mirco Troue2, Johannes Figueiredo2, Alexander Holleitner2, and Ursula Wurstbauer1 — 1Institute of Physics, University of Münster, Münster, Germany — 2Walter Schottky Institute and Physics Department, TU Munich, Garching, Germany
Homo- and hetero-bilayers of transition metal dichalcogenides host a rich variety of interlayer exciton (IX) species where the electrons and holes reside in different monolayers. [1] This leads to enhanced lifetimes of IXs and also imparts them with a permanent dipole moment. [1,2] Such IXs provide an ideal platform for exploring many body physics such as dipole-dipole interactions and Bose-Einstein condensation. [2] We have investigated IXs in a heterobilayer of MoSe2 and WSe2 encapsulated in hBN, using temperature, laser power and time dependent photoluminescence (PL) spectroscopy down to millikelvin temperatures. At lowest temperatures and exciton densities, we observe a single low energy peak in the IX PL spectrum which has been attributed to be a signature of degenerate exciton gas. [2] We observe an unexpected nearly excitation power-independent IX energies at lowest temperatures (10 mK to ~10K) that converts into the well-known dipolar blue-shift at elevated temperatures. We acknowledge financial support by DFG via WU 637/4-2 and No. HO 3324/9-2 and SPP2244.
[1] B. Miller et al., Nano Lett. 17, 5229 (2017). [2] L. Sigl et al., Phys. Rev. Research 2, 042044 (R) (2020).