Events

Quantum Materials and Devices Seminars

Probing the dark side of the exciton with time-resolved ARPES

Keshav Dani

Apr 7, 2021
10:00 am to 11:00 am | Remote

Register Here:
https://harvard.zoom.us/webinar/register/WN_q8rI_YJWS2GiLNyxVADNKA

 

About a decade ago, the discovery of monolayers of transition metal dichalcogenides opened a new frontier in the study of optically excited states in semiconductors. These materials exhibit a plethora of robust excitonic states – bound quasiparticle pairs of electrons and holes, such as bright excitons, momentum- and spin-forbidden dark excitons, and hot excitons. While optics-based experiments can access bright excitons, measuring dark excitons requires a momentum-resolving technique like ARPES – a decades-old grand challenge. Accessing excitons with ARPES is not just conceptually difficult – ‘how does one photoemit an exciton’, but also technically difficult – one needs to study micron-scale samples of atomically-thin materials, with ultrafast time-resolution, using XUV photons. In today’s talk, I will discuss the work in my lab towards these goals [1, 2, 3].

[1] T. Doherty*, A. Winchester*, et al. Nature 580 360 (2020)

[2] J. Madeo*, M. K. L. Man*, et al. Science 370 1199 (2020).

[3] M. K. L. Man*, J. Madeo*, et al. Science Advances (in press).

* equal authors

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Emily Haderer