News & Views: Hot plasmons make graphene shine

News & Views piece published in Nature Materials

A new significant research on ultrafast excitation and relaxation mechanisms in graphene, published in the current issue of “Nature Materials”, is featured in the “News & Views” section of the journal in an introductive article by ICN2 group leader Dr Klaas-Jan Tielrooij and ICFO group leader Prof. Frank Koppens.

Dr Klaas-Jan Tielrooij, leader of the ICN2 Ultrafast Dynamics in Nanoscale Systems group, and Prof. Frank Koppens, group leader at the Institute of Photonic Sciences (ICFO), published a News & Views article in Nature Materials as an introduction to highlight a paper published in the same issue of the journal.  The work they summarize is a remarkable study on the ultrafast carrier dynamics of graphene, carried out by Dr Laura Kim –from the Massachusetts Institute of Technology– and her colleagues, which provides the first experimental evidence of hot plasmon emission in graphene as a consequence of carrier excitation by ultrashort laser pulses.  

When graphene carriers are excited, carrier-carrier interactions take place on a femtosecond timescale. A cooling phase follows, which can occur through different processes, chiefly via phonon emission. According to this research, an additional relaxation (and cooling) channel exists, which involves ultrafast energy flow from excited carriers into graphene plasmons. This process leads to the emission of mid-infrared light, which increases its brightness when gold nanodisks are added.

As highlighted by Dr Tielrooij and Prof. Koppens, this study is not only noteworthy in its own rights, but also for the opportunities of new practical applications that the identified mechanism provides.

Image credit: Matteo Ceccanti