Superconductors are materials that permit electrical current to flow without energy loss. Their amazing properties form the basis for magnetic resonance imaging (MRI) devices as well as emerging technologies such as quantum computers. Most superconducting materials, however, behave as superconductors only at very low temperatures. Even so-called “high-temperature” superconductors must be cooled to −135 °C using liquid nitrogen to achieve superconductivity!
At the heart of all superconductors is the bunching of electrons into pairs. A new discovery has confirmed a long-hypothesized phase in which electrons form pairs but do not reach a superconducting state. The discovery provides fundamental new insights into a mechanism that could one day be used to design a material that is superconducting at room temperature.
One way to understand this novel state is to extend an analogy first articulated by J. Robert Schrieffer, who shared the 1972 Nobel Prize in Physics for the theory of superconductivity. In a superconductor, the motion of paired electrons is highly coordinated, similar to waltzing couples on a dance floor. In the “normal” or non-superconducting state, electrons move independently, bumping into one another occasionally and dissipating energy, creating resistance and resulting in the energy loss we observe as current flows. What the new research has identified is an in-between state where the electrons form pairs, but each pair moves independently. We may think of the electron pairs as “swing dancing,” where dancing pairs hold hands but do not move in any synchronized fashion. The discovery of a state in which electrons pair without exhibiting superconductivity is helping researchers better understand what makes a material superconductive–not just the pairing of electrons, but the behavior of the electron pairs. Researchers can now apply this key insight in their efforts to develop a room-temperature superconductor.