After 20 Years of Trying, Scientists Succeed in Doping a 1D Atomic Chain of Cuprates

 

An illustration portrays a surprisingly strong attraction between electrons in neighboring lattice sites within a 1D chain of copper oxide, or cuprate – a substance that conducts electrical current with no loss at relatively high temperatures. A research led by Stanford, SLAC and Clemson revealed this unusually strong “nearest-neighbor” attraction in a 1D cuprate chain that had been “doped” to raise the density of its free electrons. They believed that the unexpected strength of the attractions may result from relations with natural vibrations in the material’s atomic lattice, which may play a vital role in cuprate superconductivity. Credit: SCI-HUA

 

The chemically controlled chains expose an ultrastrong attraction between electrons that may help cuprate superconductors transmit electrical current with no loss at relatively high temperatures.

 

When researchers study unconventional superconductors – complex substances that conduct electricity with zero loss at relatively high temperatures – they often rely on basic models to get an understanding of what’s going on.

 

Scientists know these quantum substances get their abilities from electrons that link forces to form a sort of electron soup. But modeling this phenomenon in all its complexity would take far more time and calculating power than anyone can imagine having today. So for understanding one key class of eccentric superconductors – copper oxides, or cuprates – scientists created, for ease, a theoretical model in which the substances exists in just one dimension, as a string of atoms. They created these one-dimensional cuprates in the lab and discovered that their behavior agreed with the theory pretty well.

 

However, these 1D atomic chains lacked one thing: They could not be doped, a procedure where some atoms are swapped by others to change the number of electrons that are free to move around. Doping is one of several factors researchers can alter to tweak the behavior of substances like these, and it’s a crucial part of getting them to superconduct.

 

Vibrations Interact With 1D Cuprate Chain

An illustration of 1D copper oxide, or cuprate, chains that have been “doped” to free up some of their electrons in a research led by scientists at SLAC National Accelerator Laboratory and Stanford and Clemson universities. Copper atoms are black and oxygen atoms purple. The red springs indicate natural vibrations that shake the atomic lattice, which may help generate a surprisingly strong attraction (not shown) between neighboring electrons in the lattice. This “nearest-neighbor” attraction may play a key role in unconventional superconductivity – the ability to conduct electric current with no loss at relatively high temperatures. Credit: Greg Stewart/SLAC National Accelerator Laboratory

 

Now a research led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford and Clemson universities has produced the first 1D cuprate substance that can be doped. Their study of the doped material indicates that the most prominent proposed model of how cuprates achieve superconductivity is lacking a key ingredient: an unexpectedly strong attraction between neighboring electrons in the substance’s atomic structure, or lattice. That attraction, they told, may be the result of interactions with natural lattice vibrations.

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