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Abstract:

Over the last decade, the field of 2D materials has blossomed to include libraries of materials with diverse properties ranging from metallic to insulating and magnetic to superconducting. With the goal of engineering designer materials, researchers layer these 2D materials in heterostacks in hopes of combining desirable properties and creating new ones [1].  Of these new features, the interlayer exciton, an electron-hole pair split across two semiconducting monolayers, has drawn much attention. Interlayer exciton emits photons in wavelengths from the visible to telecom frequencies tunable with a relatively small electric field making them appealing for electro-optical modulation applications [2]. Furthermore, the two lattices combine to create a moiré potential which can confine the interlayer excitons to a periodic lattice useful for studying correlated physics phenomena [2].

Despite the exponential increase in publications focused on interlayer excitons over the past few years [3], several key questions have remained unanswered namely the radiative rate or absorption strength and the degree of confinement in moiré potential. Recently, we have addressed both these questions using electro-reflectance techniques [4] and time-resolved angle-resolved photoemission spectroscopy [5]. In this talk, I will summarize the results from the aforementioned studies and discuss how electro-reflectance techniques can be expanded to other layered systems.

[1] Geim and Grigorieva, Nature 499, 419-425 (2013)

[2] Shree et al., Nat. Rev. Phys. 3, 39-54 (2021)

[3] Web of Science analytics

[4] E. Barré et al., Science , 376, 6591 (2022)

[5] O. Karni*, E. Barré*, V. Pareek*, J. D. Georgaras*, M. K. L. Man*, C. Sahoo*, et al. Nature, 603 (2022).

Bio:

Dr. Elyse Barré is a post-doctoral researcher working in the Molecular Foundry at the Lawrence Berkeley National Laboratory in Berkeley, California. She received her bachelor’s degree in Engineering Physics at ÐÓ°ÉÔ­´´ University in 2015. She received her master’s degree and Ph.D. in Electrical Engineering at Stanford University in 2017 and 2022 respectively with support from NSERC Postgraduate scholarship.