Valleytronics and Graphene



Two interesting discoveries were made about graphene and published in the journal Nano Letters.

Electron transport in bilayer graphene shows reliance on both edge state and a non-local transport mechanism.

The study is led by professor Gil-Ho Lee and Hyeon Jeong from POSTECH’d Department of Physics. They worked with Dr. Kenji Watanabe and Dr. Takashi Taniguchi from Japan’s National Institute for Materials Science (NIMS). 

Bilayer graphene is made up of two vertically stacked graphene layers. Graphene can modulate it’s electronic band gap by using electric fields that are applied. This property is essential for electron transport. Scientists are interested in exploiting the substance in “valleytronics,” the next generation of data processing. 

A valley is a quantum state. It is an electron’s energy structure and is it’s data storage unit. Valleytronics Will enable more efficient, faster, data processing than even spintronics. 

Valleytronics is based on the “Valley Hall Effect” (VHE). This describes how the electron flow is funneled through energy states. This is known as “valleys” within a given material. 

Also discovered, “non-local resistance” Proves measurable resistance in regions, lacking direct current flow. Many previous studies consider non-local resistance as proof of the VHE. Some scientists put forward that device edge impurities can also create the observed signals. Therefore, the origin of the VHE is unknown.

Scientists are working to discover the source of non-local resistance in bilayer graphene. The team teams at POSCO-NIMS Created a dual gate graphene device. It enables precise band gap control. They compared the electrical properties of pure and natural graphene to artificially processed graphene made with reactive ion etching. 

The findings showed that non-local resistance in naturally formed Graphene met the scientists expectations. The etching processed Graphene showed non-local resistance over the original values by two times.


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