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Dynamics of photons, plasmons and electrons in 2d materials

March 28, 2016 - 11:00am
Speaker: 
Frank Koppens
Institution: 
ICFO

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 [2,3]. In addition, we apply for the first time infrared photocurrent nanoscopy to high-quality graphene devices [4]. 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 [5,6]. In addition, nano-structured sandwiches of graphene with boron nitride have resulted in high quality plasmonic systems for infrared light [7].

 

References:

[1] Photodetectors based on graphene, other two-dimensional materials and hybrid systems
F. H. L. Koppens et al. Nature Nanotechnol. 9, 780-793 (2014)

[2] Picosecond photoresponse in van der Waals heterostructures

M. Massicotte et al., Nature Nanotechnology 11 (2016)

[3] Photo-thermionic effect in vertical graphene heterostructures. Mathieu Massicotte, Peter Schmidt, FabienVialla, Kenji Watanabe, Takashi Taniguchi, Klaas-Jan Tielrooij, Frank H.L. Koppens. arXiv: 1601.04196

[4] Near-field photocurrent nanoscopy on bare and encapsulated graphene. A. Woessner, Nature Communications (2016).

[5] Thermoelectric detection of propagating plasmons in graphene

M.B. Lundeberg et al., arXiv (2016) arXiv:1601.01977
[6] Ultra-confined acoustic THz graphene plasmons revealed by photocurrent nanoscopy

P. Alonso-González et al., arXiv (2016) arXiv:1601.0575.

[7] Highly confined low-loss plasmons in graphene–boron nitride heterostructures

A. Woessner et al., Nature Materials, 14, 421-425 (2015)

 

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