A rare metal alloy, niobium-rhenium (NbRe), is showing promising signs of being a long-sought “triplet superconductor,” a material that could dramatically improve the energy efficiency of quantum computers and pave the way for new spintronic technologies. Researchers at the Norwegian University of Science and Technology (NTNU) believe they have observed properties consistent with this type of superconductivity, a finding that, if verified, could represent a significant leap forward in quantum science.
Superconductors, materials that conduct electricity with zero resistance, are already used in a variety of applications, from MRI machines to high-speed trains. However, conventional, or “singlet,” superconductors have limitations. The superconducting particles within them do not carry spin, a fundamental property of electrons. This restricts their use in spintronics – a field that aims to use electron spin, rather than charge, to process information – and in quantum systems that rely on controlling spin.
“A triplet superconductor is high on the wish list of many physicists working in the field of solid state physics,” said Professor Jacob Linder, a physicist at NTNU’s Department of Physics and QuSpin research center. “Materials that are triplet superconductors are a kind of ‘holy grail’ in quantum technology, and more specifically quantum computing.”
The Advantage of Spin: Triplet vs. Singlet Superconductivity
The key difference between singlet and triplet superconductors lies in the spin of the superconducting particles. Triplet superconductors do carry spin. This seemingly small difference has profound implications.
“The fact that triplet superconductors have spin has an important consequence. We can now transport not only electrical currents but also spin currents with absolutely zero resistance,” explained Linder. This ability to transport spin without energy loss could unlock entirely new ways to process and transmit information, potentially leading to dramatically faster and more energy-efficient computers.
Spintronics aims to leverage the spin of electrons to create faster, more efficient electronic devices. Conventional electronics rely on the flow of electric charge. By utilizing spin, spintronics promises to reduce energy consumption and increase processing speeds. Triplet superconductors could provide the foundation for realizing the full potential of spintronics.
Addressing Instability in Quantum Computing
One of the major hurdles in developing practical quantum computers is maintaining stability. Quantum states are fragile and susceptible to disruption, leading to errors in computation. Linder’s research focuses on finding materials that can stabilize these quantum states.
“One of the major challenges in quantum technology today is finding a way to perform computer operations with sufficient accuracy,” Linder stated. Triplet superconductivity offers a potential solution by providing a more robust platform for quantum information processing.
NbRe: A Promising Candidate, But Verification is Key
The NTNU team’s research, published in Physical Review Letters and highlighted as an editor’s recommendation, focuses on the alloy NbRe. Their experiments suggest that NbRe exhibits properties consistent with triplet superconductivity. However, Linder emphasizes that further research is needed to confirm these findings.
“It is still too early to conclude once and for all whether the material is a triplet superconductor,” he cautioned. “Among other things, the finding must be verified by other experimental groups. It is also necessary to carry out further triplet superconductivity tests.”
The team’s initial results are encouraging, however. “Our experimental research demonstrates that the material behaves completely differently from what we would expect for a conventional singlet superconductor,” Linder added.
Superconductivity at a Relatively High Temperature
Another promising aspect of NbRe is its superconducting transition temperature. While still extremely cold by everyday standards, NbRe superconducts at 7 Kelvin (approximately -266 degrees Celsius). This represents significantly warmer than many other potential triplet superconductors, which require temperatures close to absolute zero (1 Kelvin or -272.15 degrees Celsius) to exhibit superconductivity. A higher transition temperature makes the material more practical and attainable for real-world applications.
“Another advantage of this material is that it superconducts at a relatively high temperature,” Linder explained. This relative warmth simplifies the cooling requirements, reducing the complexity and cost of implementing the technology.
Looking Ahead
The discovery of a viable triplet superconductor could have far-reaching consequences, not only for quantum computing but also for spintronics and other advanced technologies. While the findings regarding NbRe are preliminary, they represent a significant step towards realizing the potential of these materials. The scientific community will be watching closely as researchers around the world attempt to replicate and expand upon these results, potentially unlocking a new era of energy-efficient and powerful computing.
