|
|
Physicist / Astronomer Stamps
|
O
1913 Nobel Physics prize for his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium. Onnes was interested in investigating the electrical properties of pure metals with no impurities in this newly available region of low temperatures. The question was: will the resistance increase, or decrease or remain constant when cooling the samples? He decided to work with mercury which can be repeatedly distilled at room temperature in order to obtain a pure sample. What happened was completely unpredictable: Onnes found (1911) that when cooling the pure mercury tubes to a temperature of 4.2 °K the resistance suddenly dropped to zero. He termed this phenomenon "superconductivity." He showed similar results in some other metals, for instance in tin and lead and in 1914 he established a permanent current, or what he called a "persistent supercurrent", in a superconducting coil of lead. His systematic researches on superconductivity (begun in 1911) were of extreme importance because of their bearing on the theory of electrical conduction in solids. It was 46 years before John Bardeen, Leon N. Cooper and J. Robert Schrieffer established the theoretical foundations that best explained superconductivity.
|
|
