Home > Press > A Novel Graphene Quantum Dot Structure Takes the Cake
![]() |
Scanning tunneling spectroscopy image shows that magnetically confined electrons are arranged in a wedding cake-like structure of energy levels, known as Landau levels, labeled as ll (top panel). Electrons confined to those levels create a series of insulating and conducting rings within graphene (bottom panel). Credit: NIST |
Abstract:
In a marriage of quantum science and solid-state physics, researchers at the National Institute of Standards and Technology (NIST) have used magnetic fields to confine groups of electrons to a series of concentric rings within graphene, a single layer of tightly packed carbon atoms.
This tiered “wedding cake,” which appears in images that show the energy level structure of the electrons, experimentally confirms how electrons interact in a tightly confined space according to long-untested rules of quantum mechanics. The findings could also have practical applications in quantum computing.
Graphene is a highly promising material for new electronic devices because of its mechanical strength, its excellent ability to conduct electricity and its ultrathin, essentially two-dimensional structure. For these reasons, scientists welcome any new insights on this wonder material.
The researchers, who report their findings in the Aug. 24 issue of Science, began their experiment by creating quantum dots—tiny islands that act as artificial atoms—in graphene devices cooled to just a few degrees above absolute zero.
Electrons orbit quantum dots in a way that’s very similar to how they orbit atoms. Like rungs on a ladder, they can only occupy specific energy levels according to the rules of quantum theory. But something special happened when the researchers applied a magnetic field, which further confined the electrons orbiting the quantum dot. When the applied field reached a strength of about 1 Tesla (some 100 times the typical strength of a small bar magnet), the electrons packed closer together and interacted more strongly.
As a result, the electrons rearranged themselves into a novel pattern: an alternating series of conducting and insulating concentric rings on the surface. When the researchers stacked images of the concentric rings recorded at different electron energy levels, the resulting picture resembled a wedding cake, with electron energy as the vertical dimension.
A scanning tunneling microscope, which images surfaces with atomic-scale resolution by recording the flow of electrons between different regions of the sample and the ultrasharp tip of the microscope’s stylus, revealed the structure.
“This is a textbook example of a problem—determining what the combined effect of spatial and magnetic confinement of electrons looks like—that you solve on paper when you’re first exposed to quantum mechanics, but that no one’s actually seen before,” said NIST scientist and co-author Joseph Stroscio. “The key is that graphene is a truly two-dimensional material with an exposed sea of electrons at the surface,” he added. “In previous experiments using other materials, quantum dots were buried at material interfaces so no one had been able to look inside them and see how the energy levels change when a magnetic field was applied.”
Graphene quantum dots have been proposed as fundamental components of some quantum computers.
“Since we see this behavior begin at moderate fields of just about 1 Tesla, it means that these electron-electron interactions will have to be carefully accounted for when considering certain types of graphene quantum dots for quantum computation,” said study co-author Christopher Gutiérrez, now at the University of British Columbia in Vancouver, who performed the experimental work at NIST with co-authors Fereshte Ghahari and Daniel Walkup of NIST and the University of Maryland.
This achievement also opens possibilities for graphene to act as what the researchers call a “relativistic quantum simulator.” The theory of relativity describes how objects behave when moving at or close to light speed. And electrons in graphene possess an unusual property—they move as if they are massless, like particles of light. Although electrons in graphene actually travel far slower than the speed of light, their light-like massless behavior has earned them the moniker of “relativistic” matter. The new study opens the door to creating a table-top experiment to study strongly confined relativistic matter.
Collaborators on this work included researchers from the Massachusetts Institute of Technology, Harvard University, the University of Maryland NanoCenter and the National Institute for Material Science in Ibaraki, Japan.
The measurements suggest that scientists may soon find even more exotic structures produced by the interactions of electrons confined to solid-state materials at low temperatures.
####
For more information, please click here
Contacts:
Ben P. Stein
(301) 975-2763
Copyright © National Institute of Standards and Technology (NIST)
If you have a comment, please Contact us.Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Related Links |
Related News Press |
News and information
Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025
Quantum computers simulate fundamental physics: shedding light on the building blocks of nature June 6th, 2025
A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025
Graphene/ Graphite
Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025
Breakthrough in proton barrier films using pore-free graphene oxide: Kumamoto University researchers achieve new milestone in advanced coating technologies September 13th, 2024
Quantum Physics
Quantum computers simulate fundamental physics: shedding light on the building blocks of nature June 6th, 2025
A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025
2 Dimensional Materials
Closing the gaps — MXene-coating filters can enhance performance and reusability February 28th, 2025
New 2D multifractal tools delve into Pollock's expressionism January 17th, 2025
Chainmail-like material could be the future of armor: First 2D mechanically interlocked polymer exhibits exceptional flexibility and strength January 17th, 2025
FSU researchers develop new methods to generate and improve magnetism of 2D materials December 13th, 2024
Laboratories
Govt.-Legislation/Regulation/Funding/Policy
Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025
Institute for Nanoscience hosts annual proposal planning meeting May 16th, 2025
Rice researchers harness gravity to create low-cost device for rapid cell analysis February 28th, 2025
Possible Futures
Ben-Gurion University of the Negev researchers several steps closer to harnessing patient's own T-cells to fight off cancer June 6th, 2025
Researchers unveil a groundbreaking clay-based solution to capture carbon dioxide and combat climate change June 6th, 2025
Cambridge chemists discover simple way to build bigger molecules – one carbon at a time June 6th, 2025
A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025
Chip Technology
A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025
Programmable electron-induced color router array May 14th, 2025
Enhancing power factor of p- and n-type single-walled carbon nanotubes April 25th, 2025
Ultrafast plasmon-enhanced magnetic bit switching at the nanoscale April 25th, 2025
Quantum Computing
Quantum computers simulate fundamental physics: shedding light on the building blocks of nature June 6th, 2025
Magnetism in new exotic material opens the way for robust quantum computers June 4th, 2025
Programmable electron-induced color router array May 14th, 2025
Materials/Metamaterials/Magnetoresistance
Researchers unveil a groundbreaking clay-based solution to capture carbon dioxide and combat climate change June 6th, 2025
A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025
Institute for Nanoscience hosts annual proposal planning meeting May 16th, 2025
Announcements
Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025
Quantum computers simulate fundamental physics: shedding light on the building blocks of nature June 6th, 2025
A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025
Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters
Cambridge chemists discover simple way to build bigger molecules – one carbon at a time June 6th, 2025
Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025
Quantum computers simulate fundamental physics: shedding light on the building blocks of nature June 6th, 2025
A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025
Quantum Dots/Rods
A new kind of magnetism November 17th, 2023
IOP Publishing celebrates World Quantum Day with the announcement of a special quantum collection and the winners of two prestigious quantum awards April 14th, 2023
Qubits on strong stimulants: Researchers find ways to improve the storage time of quantum information in a spin rich material January 27th, 2023
NIST’s grid of quantum islands could reveal secrets for powerful technologies November 18th, 2022
Research partnerships
HKU physicists uncover hidden order in the quantum world through deconfined quantum critical points April 25th, 2025
SMART researchers pioneer first-of-its-kind nanosensor for real-time iron detection in plants February 28th, 2025
Quantum nanoscience
Programmable electron-induced color router array May 14th, 2025
![]() |
||
![]() |
||
The latest news from around the world, FREE | ||
![]() |
![]() |
||
Premium Products | ||
![]() |
||
Only the news you want to read!
Learn More |
||
![]() |
||
Full-service, expert consulting
Learn More |
||
![]() |