Imagine a train gliding above the rails without friction, or a smartphone charger in which not a single watt is wasted. It is precisely such prospects that superconductivity opens up — a phenomenon in which electric current flows without resistance. Yet for decades it remained attainable only at extremely low temperatures requiring costly cooling with liquid helium.
A new study by scientists from Utrecht University, Leiden University and Munich brings the cherished goal closer. The work, published today in the journal Science, shows that one of the two main conditions for superconductivity may already be met at room temperature. This is an important step forward, although the full picture is not yet clear.
Superconductivity requires two things. First, electrons must combine into Cooper pairs. Second, these pairs must move in synchrony — so-called phase coherence. In ordinary superconductors both processes occur simultaneously at very low temperatures. In high-temperature materials discovered in the 1980s, the situation is different.
The scientists found that Cooper pairs in such materials form at temperatures considerably above the transition point to the superconducting state. "The 'glue' holding the pairs together is strong enough to preserve them even at room temperature," notes one of the study's leaders, Ingmar Swart. Thus, the bottleneck remains precisely the synchronous motion of the pairs.
For the measurements, the team built its own equipment capable of distinguishing the current carried by individual electrons from the current carried by pairs. This made it possible to observe directly when and how pairing occurs. The results confirm that the first key stage is achievable under ordinary conditions.
If phase coherence can be figured out, the path to room-temperature superconductivity will become real. Then ultra-efficient power lines, powerful quantum computers and magnetic levitating trains will appear without enormous cooling costs. The researchers already plan to focus on this second challenge.
The discovery does not promise an instant breakthrough, but it clearly indicates the direction to move in next. It is now clear that one of the main obstacles is surmountable — and this inspires well-founded hope.
