The doughnut-shaped carbon molecule develops stable toroidal moments when an electric voltage is applied. The image shows the distribution of the corresponding electron density.
Image Credit: AG Berakdar
Scientific Frontline: Extended "At a Glance" Summary: Quantum Control via Carbon Nanotori
The Core Concept: Researchers have discovered a method to generate and control toroidal moments—a rare class of electromagnetic dipoles—at the nanoscale using doughnut-shaped rings of carbon atoms known as nanotori.
Key Distinction/Mechanism: Unlike standard electric or magnetic dipoles, toroidal systems enclose a magnetic field but remain electrically neutral, generating no external electric or magnetic fields. By applying a constant electric field to carbon nanotori, electrons are forced into a 3D vortex around the ring, generating a stable, loss-free toroidal moment that overcomes the energy dissipation of conventional, macroscopic toroidal coils.
Major Frameworks/Components:
- Toroidal Dipoles: A third, traditionally elusive class of charge-current distributions alongside conventional electric and magnetic dipoles.
- Carbon Nanotori: Doughnut-shaped nanoscale carbon structures that host the requisite electron vortices.
- Quantum Mechanical Phases: The underlying physical states that these localized toroidal moments can directly alter without producing stray fields.
Branch of Science: Quantum Physics, Condensed Matter Physics, Nanoscale Engineering, and Computational Materials Science.
Future Application: This mechanism offers precise control over superconductors and could serve as a foundational technology for advanced quantum computing architecture, allowing current to flow efficiently with virtually zero loss.
Why It Matters: Because toroidal moments generate no external fields, they eliminate the signal noise and high energy consumption that typically plague quantum systems when standard electric or magnetic fields inadvertently excite nearby particles.
Quantum states can be precisely controlled with the help of tiny carbon rings measuring only a few nanometers in size. This is made possible by a class of rarely utilized electromagnetic dipoles called toroidal moments. Using computer simulations, physicists at Martin Luther University Halle-Wittenberg (MLU) have now found a way to generate and control these nanostructures without any loss. The findings were published in the journal npj Computational Materials and create new opportunities for quantum computer technology.
In physics, there are two well-known types of dipoles: Electric dipoles generate electric signals, such as those found in batteries and antennas. Magnetic dipoles, like a charged coil or a bar magnet, are created through moving charges or permanent magnets. These traditional dipoles are joined by a third class of charge-current distributions that, up until now, have been difficult to replicate at the molecular level: toroidal dipoles. “You can picture it like this: A coil bearing an electric current encloses a magnetic field that disappears outside the coil. Connecting the ends of the coil creates a toroidal system that is electrically neutral and generates no external electric or magnetic fields,” explains physicist Jamal Berakdar at MLU, who conducted the study with Dr. Arkamita Bandyopadhyay.
Even though researchers knew that stable toroidal moments could exist, it was unclear how to generate and control them at the nano level; problems arise when they are reduced to the nanoscale. “Conventional toroidal coils work well as long as they are large enough—for example, when they have a radius measuring 1 centimeter. However, if the coil is too small, the current does not flow efficiently in the circuit, and there are high losses,” explains Bandyopadhyay.
Researchers at MLU have used computer simulations to demonstrate how toroidal moments can be generated in so-called nanotori. These are ring-shaped structures composed of carbon atoms that look like tiny doughnuts. When a constant electric field is applied to these structures, the electrons move in a three-dimensional vortex around the ring, thereby forming a toroidal moment. “We use computer simulations to show how toroidal moments can be generated without loss at the nanoscale, as well as controlled, excited, and switched,” says Berakdar.
The findings of the study open new possibilities in the field of quantum computing. One example is the precise control of superconductors through which current can flow with virtually no loss. Existing methods often require magnetic or electric fields that, at the nanoscale, are very difficult to focus. These fields not only affect the superconductor but also excite other nearby particles. This can lead to signal noise or high energy consumption. “This problem can be circumvented by utilizing toroidal moments in carbon nanotori, as they can directly alter quantum mechanical phases,” concludes Bandyopadhyay.
Funding: The work was funded by the German Research Foundation (DFG).
Published in journal: npj Computational Materials
Title: Topology-enabled quantum toroidal moment in carbon nanotori
Authors: Arkamita Bandyopadhyay, and Jamal Berakdar
Source/Credit: Martin Luther University Halle-Wittenberg | Zum Seitenanfang
Edited by: Scientific Frontline
Reference Number: qs070726_01
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