SUTD researchers discover a Valleytronics route towards reversible computer

December 21, 2017

In many two-dimensional (2D) materials, electrons not only possess charge and spin, but further exhibits an unusual quantum feature known as "valley". Simply speaking, electrons residing in many 2D materials can live in well-separated energy minima, and the "address" describing which minima these electrons belong to is known as "valley". The use of this "valley address" to encode and process information forms the core of a new vibrant research field known as "valleytronics".

Despite much anticipation of valleytronics being a candidate for 'beyond CMOS' technology and to continue the legacy of Moore's law, its progress is severely hindered by the lack of practical designs for a valleytronic-based information processing unit. One major challenge in valleytronic is the construction of a "valley filter". Valley filter can produce electrical current composed dominantly of electrons from only one specific "valley". It serves as a fundamental building block in valleytronics.

By harnessing the unusual electrical properties of 2D materials such as few-layer black phosphorus and topological Weyl/Dirac semimetal thin films, researchers from the Singapore University of Technology and Design (SUTD) designed a versatile all-electric-controlled valley filter and demonstrated, for the first time, a concrete working design of valleytronic logic gate capable of performing the full set of two-input Boolean logics.

"A particularly remarkable finding is a previously unexplored approach of achieving logically-reversible computation by storing information in the electron's valley state," said first-author Dr Yee Sin Ang from SUTD.

Conventional digital computers process information in a logically-irreversible fashion. This leads to a serious logical issue - upon receiving a computational output, an end-user cannot unambiguously identify the original input information that produces this output.

Making digital computing logically-reversible is not only interesting in terms of fundamental information science, but also has broad applications in areas such as cryptography, signal and image processing, quantum computing, and is ultimately required to improve the energy efficiency of digital computers beyond the thermodynamic bottleneck also known as Landauer's limit. Due to its immense potentials, enormous research efforts have been devoted to the search for a practical reversible computer since the 1970s.

The traditional way of making a logically-reversible computer relies heavily on complex circuitries that inevitably generate large quantities of wasteful bits. These complex and wasteful methods have prevented reversible computing from gaining widespread industrial and commercial interests.

The key novelty of the valleytronic-based reversible logic gate proposed by SUTD researchers is that the device stores additional bits of input information in the valley state of the computational output to achieve logical-reversibility. This valleytronic approach bypasses the need of complex circuitries and significantly reduces the generation of wasteful bits. Such simple architecture is also more compatible with the ever-growing industrial and commercial demands for compact smart devices with ever-shrinking physical sizes.

Co-author and principal investigator of this research, SUTD Prof Ricky Ang, said: "The union of valleytronics, digital information processing and reversible computing may provide a new paradigm towards the future of ultimately energy-efficient computer with novel functionalities."
-end-


Singapore University of Technology and Design

Related Electrons Articles from Brightsurf:

One-way street for electrons
An international team of physicists, led by researchers of the Universities of Oldenburg and Bremen, Germany, has recorded an ultrafast film of the directed energy transport between neighbouring molecules in a nanomaterial.

Mystery solved: a 'New Kind of Electrons'
Why do certain materials emit electrons with a very specific energy?

Sticky electrons: When repulsion turns into attraction
Scientists in Vienna explain what happens at a strange 'border line' in materials science: Under certain conditions, materials change from well-known behaviour to different, partly unexplained phenomena.

Self-imaging of a molecule by its own electrons
Researchers at the Max Born Institute (MBI) have shown that high-resolution movies of molecular dynamics can be recorded using electrons ejected from the molecule by an intense laser field.

Electrons in the fast lane
Microscopic structures could further improve perovskite solar cells

Laser takes pictures of electrons in crystals
Microscopes of visible light allow to see tiny objects as living cells and their interior.

Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.

Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.

Researchers develop one-way street for electrons
The work has shown that these electron ratchets create geometric diodes that operate at room temperature and may unlock unprecedented abilities in the illusive terahertz regime.

Photons and electrons one on one
The dynamics of electrons changes ever so slightly on each interaction with a photon.

Read More: Electrons News and Electrons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.