K. Alex Müller, Innovator in Ceramic Superconductors, Dies at 95
It’s rare for a scientist to receive a Nobel Prize in Physics for discoveries made close to the age of 60, or for work done shortly before the prize is announced. But K. Alex Müller, a Swiss physicist, was 59 when he made his breakthrough, and he had to wait only 16 months before he received his Nobel Prize, in 1987, sharing it with a colleague for discovering that some ceramics can be superconductors, opening up a world of scientific and practical possibilities.
Dr. Müller died on Jan. 9 at 95, according to an announcement on Tuesday by IBM, where he had worked as a researcher. It did not say where he died.
A superconductor is a material, generally black in color, that is able to convey electricity without resistance; a current running through it will never dissipate. Superconductors have another useful property: They create powerful magnetic fields.
Superconductivity was discovered accidentally in 1911 by Heike Kamerlingh Onnes, a Dutch physicist, who received the Nobel Prize in 1913 for cooling a series of gases down to the point that they become liquids. That temperature is usually near absolute zero, defined as minus 460 degrees Fahrenheit, or 0 Kelvin.
Dr. Kamerlingh Onnes made his discovery about superconductivity while cooling mercury to minus 452 degrees Fahrenheit (about 4 Kelvin). He later found the superconducting temperature of tin (minus 453 degrees Fahrenheit) and lead (minus 447 degrees).
In the decades that followed, scientists made incremental progress at discovering materials that became superconductive at higher temperatures. But by the late 1970s, no one had found anything that did so at a temperature higher than minus 424 degrees Fahrenheit, which made the use of superconductors impractical.
In the early 1980s, Dr. Müller was working at IBM Research in Zurich — a laboratory he had been associated with since 1963 — when he became interested in finding high-temperature superconductors. To work with him, he recruited J. Georg Bednorz, whom he had advised on his Ph.D. work at the Swiss Federal Institute of Technology.
They began testing strontium titanate, an oxide that is classified as a ceramic because it is neither metal nor organic. Dr. Müller had studied the properties of strontium titanate for 15 years and thought that it could be modified to be a high-temperature superconductor. He turned out to be wrong, but he and Dr. Bednorz learned some valuable lessons and set about creating and testing other ceramics.
A quantum leap forward came in early 1986, when they created lanthanum barium copper oxide, a ceramic that became superconductive at about minus 400 degrees Fahrenheit. The publication of their results later that year ignited a frenzy in the scientific community as others raced to find ceramics that might be superconductive at even higher temperatures.
Hugo Keller, a physics professor at the University of Zurich, described Dr. Müller and Dr. Bednorz’s research as a “breakthrough.”
“Nobody expected to find superconductivity in such compounds,” he said. “Even more surprising was their high critical temperature.”
The Royal Swedish Academy of Sciences, which awards the Nobels, promptly recognized the advance as well, bestowing the physics prize jointly on Dr. Muller and Dr. Bednorz in October 1987.
Within a couple of years of the discovery, scientists identified several other ceramics that worked well as high-temperature superconductors, including yttrium barium copper oxide (roughly minus 294 degrees Fahrenheit) and bismuth strontium calcium copper oxide (roughly minus 267 degrees Fahrenheit). Those temperatures were significantly higher than the boiling point of liquid nitrogen (minus 321 degrees Fahrenheit), making them more practical to use as superconductors.
The real-world applications of these materials have been somewhat limited because ceramics can be brittle. But high-temperature superconductor cables were used to supply current to the magnets employed in both the CERN Large Hadron Collider in Switzerland and the Holbrook Superconductor Project on Long Island.
There is hope, however, that high-temperature superconductors could be used in the future to levitate trains over tracks, allowing them to move without mechanical resistance and at high speeds unheard-of today.
Karl Alex Müller was born in Basel, Switzerland, on April 20, 1927, the only child of Paul and Irma (Feigenbaum) Müller. Soon after Alex’s birth, the family moved to Salzburg, Austria, where his father was studying music. A few years later, Alex’s parents separated, and Alex and his mother moved to Dornach, Switzerland, near Basel, to live with his maternal grandparents. Alex and his mother then moved to Lugano, an Italian-speaking part of Switzerland.
His mother died when he was 11. He then spent the next seven years at Evangelical College, a boarding school in Schiers, in eastern Switzerland, only rarely seeing his father, who had remarried and had had another child. Alex’s time at the school coincided with the outbreak and end of World War II.
After completing his obligatory military service in the Swiss Army, he enrolled as a student at the Swiss Federal Institute of Technology in Zurich. The use of atomic weapons against Japan the previous year had stimulated widespread interest in nuclear physics, and his incoming freshman class was three times the usual size, beginning studies in what was known as the “atom bomb semester,” Dr. Müller recalled in an autobiographical sketch for the Nobel committee.
At the institute, he studied under Wolfgang Pauli, an Austrian physicist who won the Nobel Prize in 1945, and Paul Scherrer, a Swiss physicist who would later have a prestigious research and engineering institute named for him.
After working for a year in an institute department specializing in industrial research, Dr. Muller entered the doctoral program there and obtained his Ph.D. in 1957.
He worked for the Battelle Memorial Institute in Geneva from 1958 to 1963. He was then hired at IBM Research in Zurich. During this time he was also a lecturer and professor at the University of Zurich. He was named an IBM Fellow in 1982.
Information about his survivors was not immediately available.
Though the discovery of high-temperature superconductors was well received by the scientific community, the approach and the materials that Dr. Müller and Dr. Bednorz used were unorthodox, so much so that they decided to keep them a secret, even from their colleagues; they were afraid they’d be ridiculed.
As Dr. Bednorz explained in a 2015 interview with EP News, a CERN newsletter, “Thankfully, our colleagues working on semiconductors allowed us to use their equipment after they had left for the evening. Surprisingly, during the day, nobody noticed that many of the materials I worked with were sometimes black because they were conductors.”