Scattering-Resistant Valley Valve
Jia-Huei,Jiang1*, G. Y. Wu1,2
1Department of Physics, National Tsing-Hua University, Hsin-Chu, Taiwan
2Department of Electrical Engineering, National Tsing-Hua University, Hsin-Chu, Taiwan
* presenting author:Jia-Huei Jiang,
Graphene electrons carry the novel degree of freedom known as valley pseudospin that could be used to implement valleytronics - electronics with valley pseudospin being the information carrier.
Our group designed an all electrically driven valley valve that filters current due to the so-called “valley-orbit interaction (VOI)”, which couples valley pseudospin to an in-plane, transverse electric field and is an analogue of spin-orbit interaction (SOI).
In this study we simulate the valve in both monolayer graphene armchair nanoribbon (MLAGNR) and square-lattice nanoribbon systems.The basic unit of a valve consists of a pair of valley-filters with in-plane, transverse DC electric fields of each aligned in parallel or anti-parallel. A filter specializes in “polarizing” (the incident) electrons to one of the valleys; a second filter then allows passage of or blocks electrons from the first depending on the parallelism or anti-parallelism, respectively.
Impurity scattering is an important issue in mesoscopic transport studies. Owing to the great momentum change it requires to “flip” the valley pseudospin, our MLAGNR-based valley valve is a natural candidate for robust logic gate. The same transport studies were done on the square-lattice nanoribbon system, which has only one “valley” and therefore no valley-protection is expected, to provide a contrast.
Along with scattering studies, many experimentally important concerns such as channel misalignment were studied.

Keywords: graphene, valley-orbit interaction, Rashba, valley filter, recursive Green’s function