Superconductors Beyond 1-2-3

Abstract

In 1986 physicists K. Alex Mueller and J. Georg Bednorz of the IBM Zuerich Research Laboratory realized that La-Ba-Cu ceramics were the key to developing a new class of high-temperature superconductors that would revitalize superconductivity research and technology. Their discovery began one of the most startling revolutions in solid-state physics. In February, 1987, Maw-Kuen Wu of the University of Alabama, Ching-Wu (Paul) Chu of the University of Houston and their co-workers replaced lanthanum in the Bednorz-Mueller compound with yttrium--a smaller rare-earth element--to form a superconductor whose transition temperature was 90 kelvins. Soon after, R.Bruce van Dover, Bertram Batlogg and the author at AT T Bell Laboratories were the first to determine that the superconductor was the chemical compound now known as 1-2-3 because of the ratio of yttrium to barium to copper atoms. The 1-2-3 material was the first superconductor with a transition temperature above 77 kelvins and therefore could be cooled easily and inexpensively in a bath of liquid nitrogen. During the past four years the efforts of thousands of investigators around the world have produced about a dozen superconductors that have transition temperatures above 40 kelvins as well as a handful above 77 kelvins. So far the highestmore » transition temperature--which was achieved in a compound composed of thallium, barium, calcium, copper and oxygen--is an astounding 125 kelvins.« less