Since the first high-temperature superconducting materials, known as the cuprates, were discovered in 1986, researchers have struggled to explain their properties and to find materials with even higher superconducting transition temperatures (Tc’s). One puzzle has been the cuprates’ wide variation in Tc, ranging from below 10 K to above 130 K. Now Masatoshi Imada of Waseda University in Japan and his colleagues have used first-principles calculations to determine the order parameters—which measure the density of superconducting electrons—for four cuprate materials and have predicted the Tc’s based on those order parameters [1]. The researchers have also found what they believe is the fundamental parameter that determines Tc in a given material, which they hope will lead to the development of higher-temperature superconductors.
For each material, Imada and his colleagues applied the basic principles of quantum mechanics, focusing on the planes of copper and oxygen atoms that are known to host the superconducting electrons. They used a combination of numerical techniques, including one supplemented by machine learning, and did not require any adjustable parameters. Graphite Composite Fishing Rod
The four calculated order parameters agreed with experiments, including their dependence on doping (slight variations in composition), suggesting that the team’s model had captured fundamental aspects of cuprate superconductivity. The researchers found that the order parameter in each case is determined by the effective repulsion energy between two electrons located at the same atomic site in the crystal divided by the electron kinetic energy. This suggests that materials exhibiting stronger electron–electron repulsion should sustain larger superconducting currents and have higher Tc’s. It also supports a particular mechanism for electron pairing that leads to superconductivity—a counterintuitive concept known as attraction by repulsion.
David Ehrenstein is a Senior Editor for Physics Magazine.
Michael Thobias Schmid, Jean-Baptiste Morée, Ryui Kaneko, Youhei Yamaji, and Masatoshi Imada
Nuclear magnetic resonance spectroscopy offers strong evidence that YPtBi can exhibit topological superconductivity, a property that could be harnessed to build quantum computers. Read More »
Researchers have achieved superconductivity in a ternary hydride, widening the material possibilities for high-temperature superconductivity studies. Read More »
Experiments on a family of cuprate superconductors resolve discrepancies in previous work and elucidate why the critical temperature varies with pressure. Read More »
Michael Thobias Schmid, Jean-Baptiste Morée, Ryui Kaneko, Youhei Yamaji, and Masatoshi Imada
The volume of the sounds produced when a fluid jet hits the surface of a liquid depends on the shape of the jet.
Disease contagion is suppressed when different social groups have a large overlap in membership.
Experiments reveal that the boundaries between magnetic domains in a multilayered magnetic metal can move faster than sound, confirming a previous prediction.
Sign up to receive weekly email alerts from Physics Magazine.
Graphite Plate Electrode Use of the American Physical Society websites and journals implies that the user has read and agrees to our Terms and Conditions and any applicable Subscription Agreement.