Physicists have discovered that electrons in certain superconducting materials can bind into pairs even at room temperature, resolving a decades-old scientific debate and clarifying the hurdles facing zero-resistance electricity, according to research published in the journal Science.
Led by scientists from Utrecht University, Leiden University and Ludwig Maximilian University of Munich, the researchers examined copper-based materials known as cuprates. These compounds have long puzzled physicists because they transition into superconductors at significantly higher temperatures than traditional metals, though practical applications still require extreme refrigeration.
Two steps toward zero resistance
Superconductivity allows an electrical current to move without resistance or heat dissipation, a property that could transform electric grids, medical imaging and quantum computing. Achieving the state requires two physical milestones: individual electrons must join into Cooper pairs, and those pairs must then move in unison, a condition known as phase coherence.
In standard low-temperature superconductors discovered more than a century ago, both events happen simultaneously at temperatures near absolute zero, often around minus 260 degrees Celsius. However, the new experiments show that in high-temperature cuprates, electron pairing decouples from phase coherence. The electron bonds prove strong enough to form and persist at ambient room temperatures, well above the point where zero-resistance conduction actually begins.
“This is really good news,” said research leader Ingmar Swart of Utrecht University. “We show that one of the two key conditions for superconductivity can be met at room temperature. If that weren’t possible, room-temperature superconductivity would be out of reach altogether.”
Listening to electrical noise
To detect the microscopic interactions, first authors Maialen Ortego Larrazabal and Jiasen Niu built specialized measuring apparatus capable of tracking shot noise—tiny fluctuations in electric current produced by arriving charges. Using scanning tunneling microscopy on crystals of the cuprate BSCCO cooled to near absolute zero, the team distinguished between current carried by solo electrons and current moved by Cooper pairs.
The measurements targeted the pseudogap, a long-debated state in cuprates marked by an apparent deficit of electrons at specific energy levels. The team discovered that shot noise rose precisely at the energy threshold of the pseudogap, indicating that the gap directly reflects the creation of electron pairs rather than an unrelated physical process.
To verify the mechanism, the scientists exposed the crystals to magnetic fields reaching six tesla. The magnetic field suppressed the electron pairing, dropping the recorded noise back down to levels typical of single electrons while leaving the broader pattern of electron depletion intact.
The remaining obstacle
While the findings show that robust electron pairing can occur at everyday temperatures, cuprates still do not conduct electricity without resistance until chilled to roughly minus 173 degrees Celsius. Because the electron pairs are already present at room temperature, researchers concluded that achieving phase coherence is the sole remaining bottleneck preventing ambient superconductivity.
The study provides materials scientists with a defined target. Rather than trying to force electrons to pair up, future investigations can concentrate specifically on understanding and improving how those pairs coordinate their motion.
“If we understand phase coherence, it may point to a path toward superconductivity at higher temperatures,” Swart said.
