JQI Seminar 3/28/16 - Frank Koppens

"Dynamics of photons, plasmons and electrons in 2d materials"

Speaker: Frank Koppens, ICFO

Abstract: The optoelectronic response of two-dimensional (2D) crystals, such as graphene and transition metal dichalcogenides (TMDs), is currently subject to intensive investigations. Owing to its gapless character, extraordinary nano-photonic properties and ultrafast carrier dynamics, graphene is a promising material for quantum nano-optoelectronics. Vertically assembling graphene with TMDs in so-called van der Waals heterostructures allows the creation of novel and versatile quantum and nano-optoelectronic devices that combine the complementary properties of their constituent materials.



Here we present a various new device capabilities, varying from quantum nano-photonic devices to ultra-fast and broadband electrical detectors. We applied femtosecond time-resolved photocurrent measurements on 2d material heterostructures, which reveals the charge dynamics across TMD and graphene layers directly in the time domain. In addition, we apply for the first time infrared photocurrent nanoscopy to high-quality graphene devices. Using this technique, we image the plasmon-voltage conversion in real space, where a single graphene sheet serves simultaneously as the plasmonic medium and detector. In addition, nano-structured sandwiches of graphene with boron nitride have resulted in high quality plasmonic systems for infrared light.