A team of researchers at the University of California led by physicists have observed, characterized and controlled dark trions in a semiconductor named tungsten diselenide (WSe2) which is a feat that could increase the capacity and the form of information transmission. The study has been published in the Physical Review Letters.
In semiconductors like WSe2, a trion is a quantum bound state containing three charged particles. A negative trion has two electrons and one hole whereas a positive trion contains two holes and one electron. A hole is a vacancy in a semiconductor and behaves like a positively charged particle and a trion having 3 interacting particles can carry much more information than a single electron can carry. Electronics today use a single electron to conduct electricity and transmit information. However, trions have a net electric charge and they can be controlled with the help of an electric field. It is possible to control their motion and thus use as an information carrier. In addition to it, they also have controllable spin, momentum and a rich internal structure which can be used to encode information.
On the basis of spin configuration, they can be configured as dark trions and bright trions. A hole and electron in opposite spins are bright trions whereas hole and electron in the same configuration are called dark trions. Bright trions can couple to light strongly and can emit light efficiently means they decay quickly and dark trions couple weakly to light and they decay much more slowly as compared to bright trions. It has a life close to 100 times longer than bright trions and enables transmission of information over a longer distance.
Chun Hung, an assistant professor of physics and astronomy at UC Riverside says that we can allow writing and reading of trion information by light and that they can generate bright and dark trions and control the information that we can encode. Using dark trions for their long life we can realize the information transmission by trions as it allows more information transfer than an individual electron.
They used a single layer of WSe2 atoms like a graphite sheet because dark trions energy level in WSe2 lies below the energy level of bright trions. The dark trions can, therefore, accumulate a large population, enabling their detection. Lui explains that most of the trion research groups focus on bright trions because they emit light which can be measured.
However, researchers here have a focus on dark trions and how they behave under charge conditions in WSe2 device. They managed to demonstrate the continuous tuning from positive dark trions to negative dark trions by adjusting external voltage and confirm the dark trions by distinct spin configuration from bright trions. Our technology will be greatly enriched by using trions for information transmission. The researchers intend to demonstrate the first prototype using dark trions.