Posts Tagged ‘resonating-valence-bond’

High-Temperature Superconductivity

September 7, 2007

In 1986, a new class of materials, called “cuprate superconductors,” was discovered by Karl Muller and Johannes Bednorz, which displayed superconductivity (the flow of electricity at zero resistance) at much higher temperatures than had ever previously been found. The discovery raised the possibility of materials that could super-conduct at ordinary room temperatures, which would clearly have great technological implications. Muller and Bednorz were awarded the Nobel Prize in Physics in 1987, which stands as the shortest period ever between a discovery and a Nobel prize.

I was a graduate student at Princeton when the news of high-temperature superconductivity broke, and my Ph.D. advisor was Philip W. Anderson, the 1977 Nobel Laureate in physics who at the time was already probably the most famous and respected condensed matter theorist in the world. (One recent study claimed to show that Anderson is the “most creative physicist in the world;” I found the method of the study highly dubious, but the conclusion is not unreasonable.) Anderson nearly immediately proposed a version of his “Resonating-Valence-Bond” theory for the superconductors, and trying to develop a complete theory has been his primary preoccupation ever since.


To give you an idea of the excitement in 1987, take a look at this article, looking back at the March 1987 meeting of the American Physical Society in New York City, characterized as the “Woodstock of Physics.”

I was at that meeting, and as one of Anderson’s students, I was definitely at the epicenter of the excitement, but I was actually rather turned off by the whole atmosphere, and I avoided working on the subject too seriously, focusing instead on neural networks and spin glass theory. (As I mentioned in this post, Anderson also made seminal contributions to those fields, and he let me work on whatever I was interested in.) Nevertheless, it was impossible to avoid being influenced, and I did eventually work on a few papers related to the theory of high-temperature superconductivity.

Sadly, the hopes for room temperature cuprate super-conductivity faded with time, and no cuprates have been discovered which super-conduct above 138 degrees Kelvin. And although our understanding of the materials has improved with time, there is still also considerable controversy about the mechanism causing the superconductivity.

See this post for more information about the Hubbard Model, which underlies the physics of the cuprates.