Researches from Swiss EMPA, the Max Planck Institute and other contributors have succeeded in creating two localized quantum states in one material by expanding the width of a graphene nano ribbon from seven to nine atoms. The discovery yields implications for the future of nano-electronics, spintronics and quantum computing.
Swiss Federal Laboratories for Materials Science and Technology
Max Planck Institute for Polymer Research
Quantum states are a wave pattern of probability. Therefor different quantum states = different wave patterns capable of transmitting energy and information in different ways. This is the whole reason behind the recent gold rush in quantum materials – they have the potential to revolutionize electronics by storing energy and information inside of matter itself.
a special protected zone is created at this transition that differs electronically from the central ribbon
This graphene ribbon with two special localized quantum states – one on the inside and one on the fringes can used for semiconductors metals, insulators and maybe even in quantum computers.
Researchers discovered that every change they made to the Nanoribbons width could produce a new quantum state. So they decided to keep alternating the width essentially creating a chain of quantum states. This feature allows areas on the nanoribbon to be fine tuned like a conductor or semiconductor with different band gaps (energy levels)
“The importance of this development is also underlined by the fact that a research group at the University of California, Berkeley, came to similar results independently of us,” said Gröning.
Given this new discovery Graphene nano-ribbons could potentially be utilized for the fabrication of nano-transistors 1000 times smaller then current transistors. A transistor is the piece of a computer or other hardware that amplifies a signal. It is the first on the way to the holy grail of nano-electronics.
Graphene is renown for its supreme conductivity so with the addition of compartmentalized quantum states you have a versatile material that can both conduct electricity very well and at the same time maintain that electricity in a complex differentiated form which is perfect for nano-transistors.
Transistors also need a large enough energy differential to switch between broadcasting a 1 or 0. The good thing about this new graphene nanoribbon is that the energy levels can pretty much be set at will by changing the materials width.
However, in order for this nano-transistor to function properly thousands of atoms will need to be set in just the right place. That is a difficult hurdle for researchers to contend with and will certainly require co-operation across many disciplines i.e. physics, computer science, engineering etc.
“This is based on complex, interdisciplinary research,” says Gröning. “Researchers from different disciplines in Dübendorf, Mainz, Dresden, and Troy (USA) worked together – from theoretical understanding and specific knowledge of how precursor molecules have to be built and how structures on surfaces can be selectively grown to structural and electronic analysis using a scanning tunneling microscope.”
Under the influence of a magnetic field Each quantum state also displays a property called “spin” which could be used in the emerging field of “spintronics”. By shooting magnetic fields from a bunch of different angles you can “program” information in to the electron as subtle variations in spin.
Aside from implications in nano-electronics and spintronics graphene nano-ribbons have even more potential in the extraordinary field of quantum computing.
“We have observed that topological end states occur at the ends of certain quantum chains. This offers the possibility of using them as elements of so-called qubits – the complex, interlocked states in a quantum computer,” explains Oliver Gröning.
“Whether this potential can actually be exploited for future quantum computers remains to be seen, however. It is not enough to create localized topological states in the nano-ribbons – these would also have to be coupled with other materials such as superconductors in such a way that the conditions for qubits are actually met.”