Magnetism and Superconductivity: An Unexpected Alliance express
Using laser spectroscopy — a method akin to listening to the echo from a crystal — physicists examined the layered material. They found regions where electrons move freely (Fermi pockets) and noticed that each such region behaves in its own way.
Previously, magnetic order — where electron spins line up in a strict row — was considered an enemy of superconductivity, making it hard for electrons to pair up. But here, the two not only coexist: superconductivity blossoms right inside the magnetized zone. Magnetism doesn't hinder but rather seems to accompany the paired dance of electrons, like a stern teacher who suddenly begins to play along with a student duet.
Upon transitioning to the superconducting state, the system's entropy (a measure of disorder) drops sharply — order increases. And here's an unexpected twist: in one layer, the energy gap (the threshold to break a pair) reached 42 meV — anomalously high for such a material. This discovery overturns theories developed by Bardeen and Landau, showing that the standard model is too simplistic to describe high-temperature superconductivity. The practical goal: lossless wires.
Original abstract
as written by the authors arXiv:2606.08643
The intricate relationship between high temperature superconductivity and antiferromagnetic order in cuprates, and the fundamental origin of electron pairing remain open questions. By utilizing high-resolution laser-based spatially-resolved angle-resolved photoemission spectroscopy, we investigate the seven-layer $$Bi_{2}Sr_{2}Ca_{6}Cu_{7}O_{18+\delta}$$ (Bi2267) and identify a cuprate system that consists of multiple hole Fermi pockets. The observed Fermi pockets exhibit pronounced momentum-, temperature- and Fermi surface-dependent energy gaps. Crucially, high temperature superconductivity with a critical temperature ($$T_{\mathrm{c}}$$) of $$\sim$$75 K emerges in a system with multiple Fermi pockets and the presence of strong antiferromagnetic order and correlations. In particular, substantial electron pairing is observed along the Fermi pocket with an energy gap up to $$\sim$$42 meV in lightly-doped CuO$$_{2}$$ planes ($$p\sim$$0.05). These findings challenge the conventional understanding of the roles of the nodal and antinodal electronic states in driving high-temperature superconductivity. They show that superconductivity and antiferromagnetism can coexist in a cuprate with multiple Fermi pockets, offering further insights into the pairing mechanism in cuprate superconductors.
The material is a cuprate — the first type of superconductor to work with liquid nitrogen cooling (–196°C). Their discovery in 1986 caused a sensation comparable to the space race, spawning an avalanche of documentaries.
In science fiction, superconductors are the key to levitating trains and eternal energy. The discovery of their alliance with magnetism makes these dreams a bit more real.