Good news! Maybe, with the help of AI/machine learning we will also discover better superconducting materials.
Forget about all the nonsense of the unreliable and environmentally unfriendly euphemistically called renewable energy if we can make high-temperature superconductivity to work! Renewable energy is the biggest scam of our time and in more than a generation!
"Researchers have found quantitative evidence for a mechanism long predicted to be responsible for high-temperature superconductivity. ... the team used quantum microscopy to study a high-temperature superconductor called bismuth strontium calcium copper oxide (BSCCO). The work reveals that electrons in this material appear to enter a superfluid state due to strong electron pairing, which then allows them to move without any dissipation. ...
One possible theory ... involves a quantum phenomenon called superexchange. Unlike the more familiar exchange interaction, which affects electrons that are physically close enough to have overlapping quantum-mechanical wavefunctions, superexchange does not require overlap. Instead, it stems from the electrons “hopping” from the copper atom at one lattice site in a crystalline material to another copper atom at the next site ...
One possible theory ... involves a quantum phenomenon called superexchange. Unlike the more familiar exchange interaction, which affects electrons that are physically close enough to have overlapping quantum-mechanical wavefunctions, superexchange does not require overlap. Instead, it stems from the electrons “hopping” from the copper atom at one lattice site in a crystalline material to another copper atom at the next site ...
A key point in ... superexchange theory is that it implies that electrons seek out situations in which they can more optimally hop – for example, when the spins of neighbouring electrons point in opposite directions, establishing a regular spin-up/spin-down pattern. ...
Until now, it had been difficult to test such a theory, but ... using a modified scanning tunnelling microscope (STM) with a superconducting tip rather than the usual normal metallic one. By sweeping this superconducting tip across a sample of BSCCO, they were able to measure a current of electron pairs, rather than just a current of individual electrons. This allowed them to map the density of Cooper pairs surrounding each atom – a direct measure of superconductivity. ..."
Until now, it had been difficult to test such a theory, but ... using a modified scanning tunnelling microscope (STM) with a superconducting tip rather than the usual normal metallic one. By sweeping this superconducting tip across a sample of BSCCO, they were able to measure a current of electron pairs, rather than just a current of individual electrons. This allowed them to map the density of Cooper pairs surrounding each atom – a direct measure of superconductivity. ..."
From the significance and abstract:
"Significance
Charge-transfer superexchange interactions between electrons on adjacent Cu sites have long been hypothesized to generate the intense spin-singlet electron-pair formation in cuprate superconductors. But this concept is unproven, partly because there existed no analogue isotope effect in which one could controllably vary the charge-transfer energy E(r) and measure the changes in the electron-pair condensate Ψ. Our concept is to visualize both E(r) and nP(r)=|Ψ|2 directly at atomic scale and as a function of varying apical oxygen displacements δ(r) that occur in Bi2Sr2CaCu2O8+x. These data provide access to controllable variations in E(r) and resultant effects on nP(r), yielding dnP/dE≈− 0.81±0.17 eV−1. This compares with recent prediction dnP/dE≈−0.9 eV−1 for superexchange-mediated electron pairing in Bi2Sr2CaCu2O8+x, indicating that charge-transfer superexchange is the electron-pairing mechanism in hole-doped superconductor Bi2Sr2CaCu2O8+x.
Abstract
The elementary CuO2 plane sustaining cuprate high-temperature superconductivity occurs typically at the base of a periodic array of edge-sharing CuO5 pyramids. Virtual transitions of electrons between adjacent planar Cu and O atoms, occurring at a rate t/ℏ and across the charge-transfer energy gap E, generate “superexchange” spin–spin interactions of energy J≈4t4/E3 in an antiferromagnetic correlated-insulator state. However, hole doping this CuO2 plane converts this into a very-high-temperature superconducting state whose electron pairing is exceptional. A leading proposal ... it preserves pair-forming superexchange interactions governed by the charge-transfer energy scale E. To explore this hypothesis directly at atomic scale, we combine single-electron and electron-pair (Josephson) scanning tunneling microscopy to visualize the interplay of E and the electron-pair density nP in Bi2Sr2CaCu2O8+x. The responses of both E and nP to alterations in the distance δ between planar Cu and apical O atoms are then determined. These data reveal the empirical crux of strongly correlated superconductivity in CuO2, the response of the electron-pair condensate to varying the charge-transfer energy. Concurrence of predictions from strong-correlation theory for hole-doped charge-transfer insulators with these observations indicates that charge-transfer superexchange is the electron-pairing mechanism of superconductive Bi2Sr2CaCu2O8+x."
Moder art? Fig. 1 Superexchange magnetic interactions in transition-metal oxides. (A) Schematic representation of CuO5 pyramids whose bases comprise the CuO2 plane.
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