Valley-transistors in two-dimensional materials – materials for all-optical quantum technology

April 23, 2023

(Nanowerk News) Researchers from the Indian Institute of Technology Bombay have devised a new method for constructing valley transistors in two-dimensional materials using brief pulses of light, bringing us closer to realizing practical all-optical quantum technology.

Transistors, important components in electronics, control the flow of electric current and turn it on and off as needed. These on-off states represent the binary units, or bits, that make a conventional computer work. Nanotechnology has advanced electronic devices by shrinking them and increasing their performance. Graphene, a thin atomic material with a hexagonal carbon atom structure, is a prime example of the potential of nanotechnology.

Scientists have synthesized another two-dimensional material inspired by graphene, which has the potential to revolutionize emerging quantum technologies. The electrons in these materials have an additional property called valley pseudospin, which is associated with a local energy minima. These materials exhibit two valleys that can be seen as binary units, such as 0 and 1, and their superposition, which is very important for quantum technology.

These valleys can be harnessed to encode, process and store quantum information at room temperature, enabling secure encryption and new computational methods not possible with conventional computers. Additionally, quantum technology offers simulation tools that facilitate the development of innovative materials and drugs. Illustration of a valley transistor in two-dimensional material. (Image courtesy of the researchers)

The realization of the valley transistor at room temperature is very important for practical quantum technology. The valley transistor is a switch that allows the valley selection operation to be switched between valleys as needed. However, the short valley lifetime poses a significant challenge for fabricating valley transistors.

Recent publications in Physical Review Applied (“All-Optical Ultrafast Valley Switching in Two-Dimensional Materials”) offers a solution to this problem. Researchers Navdeep Rana and Gopal Dixit have developed a method for fabricating a valley transistor in two-dimensional materials using a series of three short pulses of light to control the valley operation.

The researchers demonstrated that their control protocol is robust and universal, as they observed valley transistors in graphene and molybdenum disulfide, another two-dimensional material.

This work goes beyond the current valleytronics paradigm and introduces the possibility of valley transistors operating at the petahertz (PHz) level, significantly exceeding the speed of contemporary computing.

According to Prof. Gopal Dixit, “With the availability of valley transistors in 2D materials, mini quantum computers operating at room temperature, just like regular computers, could become a reality in the near future.”

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