“I believe that a discovery that I have made may make room-temperature superconductivity a reality.“
-Linus Pauling, June 1990
In the late 1980s, as Linus Pauling neared his ninetieth birthday, he became interested in a new and exciting scientific endeavor: high-temperature superconductivity. While most of the field’s researchers at that time were focusing on the use of ceramics to promote superconductivity, Pauling decided to focus more on techniques for raising the temperature at which materials became superconducting in order to facilitate their usage in industrial and research settings. High-temperature superconductivity, or high-Tc, was a technique discovered in 1986, so in early 1988, when Pauling took up the topic, the field was still wide open to exploration.
So what is high-temperature superconductivity? According to a 1988 business agreement drawn up between Pauling and IBM, the definition of a “superconducting product” is “any product which contains any material which loses substantially all electrical resistance below a transition temperature above 77 degrees Kelvin.” Basically, according to this description, a superconductor is a substance that loses electrical resistance when heated to a point between 77 degrees Kelvin and some higher temperature.
(It is important to note that the high temperatures being discussed in the context of superconductivity are actually quite cold: 77 degrees Kelvin translates to -196 degrees Celsius. Superconductivity has traditionally been observed at temperatures near absolute zero; achieving it at something near room temperature would constitute a major scientific breakthrough.)
Pauling’s first step in exploring specifically high-temperature superconductors was to contact Dr. Zelek Herman, a biochemistry professor at Stanford and close colleague of Pauling’s at the Linus Pauling Institute of Science and Medicine (LPISM). Pauling’s somewhat unusual request was that Herman create a few color slides for him of the cover of American Scientist. The particular issue that he wanted depicted the structure of a high-temperature superconductor.
A month later, Pauling wrote to Herman again, this time about the possibility of obtaining a Naval Research grant to fund an investigation of the “resonating valence bond theory of superconductivity.” In developing the proposal, Pauling emphasized the importance of both fluxon theory and a method of calculating interaction with phonons by using the relation between bond length and bond number. The latter method had been formulated by Pauling in 1947.
According to Pauling, an idea for creating a superconductor occurred to him while he was thinking one day about how Damascus steel was made for swords in the Middle Ages. The exact process by which Damascus steel was originally fabricated is unknown, but one way of reproducing it is through billet welding, where layers of steel are folded over and over and then stretched until a desired thickness is reached.
In February 1988, Pauling decided to apply this method to the building of a superconductor, using lead and a malleable plastic. The idea was to see if he and his associates could get the lead thin enough to become superconducting. Pauling named his idea, “A method of fabricating a composite containing filaments of a superconducting material with diameter and cross-sectional shape such as to confer on the material improved properties, such as increase in the characteristic superconducting temperature.”
Pauling believed his superconductor would work because of a process of phonon dampening, which consisted of taking a conductive metal such as tin, drawing it to a very fine diameter, specifically 10-20 angstroms (one angstrom is equivalent to one-ten billionth of a meter) then insulating the metal with non-conductive material, such as glass. Doing so would raise the superconductive temperature, or Tc, of the metal. Pauling worked on the project together with LPISM associates at a facility that the Institute leased at the Stanford Industrial Park in Palo Alto, California.
As the work progressed, Zelek Herman developed a creative way of collecting material for the superconductor. His method called for inverting a bicycle, taking the tire off of one wheel, setting the wheel on a block of wood, heating a tin fiber above a furnace with torches, turning the wheel using the bicycle’s pedals, and collecting a thin strand of material on the rim of the wheel. Pauling was very engaged in the process and would occasionally drop by to assist in the experimentation, sometimes by wielding the torch used in stretching the borosilicated tin while standing over an 800-degree furnace.
Many pages in Pauling’s research notebook from that time show that he was likewise researching and working on calculations related to superconductors. The calculations first start to appear in February 1988 and, by Spring, he believed he had enough material to patent his idea. He filed a patent application for his “Technique for Increasing the Critical Temperature of Superconducting Materials” on May 31, 1988.