Optical valley Hall effect in gapped graphene for infrared and terahertz light photodetection

Project Information

VHPC

Grant agreement ID: 747927

DOI

10.3030/747927

Project closed

EC signature date 21 March 2017

Start date 22 August 2017

End date 21 August 2019

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 158 121,60

EU contribution

€ 158 121,60

Coordinated by

FUNDACIO INSTITUT DE CIENCIES FOTONIQUES
Spain

Periodic Reporting for period 1 - VHPC (Optical valley Hall effect in gapped graphene for infrared and terahertz light photodetection)

Reporting period: 2017-08-22 to 2019-08-21

Summary of the context and overall objectives of the project

Graphene, with ultrahigh carrier mobility and ultrafast optoelectronic signal processing ability, has great potential as a carrier of valley degree of freedom and is very promising for both fundamental research and practical application of valleytronics. Therefore, successfully manipulating valley pseudospin of electrons in graphene would greatly advance the study of valleytronics. However, in contrast to the recent progresses on Transition metal dichalcogenide monolayers, the optical and opto-electric valley physics with gapped graphene has never been experimentally studied before. More importantly, the phenomena of valley optoelectronics in gapped graphene are very different from what was studied already with MoS2 in visible light range. It includes Berry effects that are controlled by infrared and terahertz (THz) light, which are orders of magnitude stronger (due to its small gap) and also has great practical applications in photodetection in this important wavelength range with under-developed photodetectors.
Our overall objectives include Identifying and quantification extremely-high valley Hall photoconductivity, Unravelling time-resolved dynamics of valley optoelectronics in graphene and Optimizing infrared and THz Berry photodetectors.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We have observed valley Hall voltage in bilayer graphene with inversion symmetry broken by out-of-plane electrical field. By tuning this field, we further observed an evolution of Berry curvature from Hall resistivity change. Our measurement is a direct probe on trajectories of electrons at one valley, which are pre-selected by excitation from circularly polarized light. Large Berry curvature and few scattering centers in graphene lead to giant, intrinsic valley Hall conductivity.
We are still preparing our paper for journal, so our dissemination is still on the way. However, we have already attended several conferences to disseminate our result to scientific community. For example, I attended Graphene 2019 in Rome and gave a talk about the result of our project. I am invited to Singapore to give a talk about our project in this November.
We will organize a workshop regarding topological physics in the future to further disseminate our result to young student. In the future, we will broadcast our result in a more general way to greater audients, including general people in all fields.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We for the first time have observed evolution of Berry curvatures. This is important for testing Berry curvature in different topological materials, especially for artificial topological materials. This is very important as designing topological materials will enable us to reach application of dissipationless electronics. This is the dream of scientists.

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