Condensed Matter Physics - History - Classical Physics

Classical Physics

One of the first studies of condensed states of matter was by English chemist Humphry Davy, when he observed that of the forty chemical elements known at the time, twenty-six had metallic properties such as lustre, ductility and high electrical and thermal conductivity. This indicated that the atoms in Dalton's atomic theory were not indivisible as Dalton claimed, but had inner structure. Davy further claimed that elements that were then believed to be gases, such as nitrogen and hydrogen could be liquified under the right conditions and would then behave as metals.

In 1823, Michael Faraday, then an assistant in Davy's lab, successfully liquified chlorine and went on to liquify all known gaseous elements, with the exception of nitrogen, hydrogen and oxygen. Shortly after, in 1869, Irish chemist Thomas Andrews studied the phase transition from a liquid to a gas and coined the term critical point to describe the instant at which a gas and a liquid were indistinguishable as phases, and Dutch physicist Johannes van der Waals supplied the theoretical framework which allowed the prediction of critical behavior based on measurements at much higher temperatures. By 1908, James Dewar and H. Kamerlingh Onnes were successfully able to liquify hydrogen and then newly-discovered helium, respectively.

Paul Drude proposed the first theoretical model for a classical electron moving through a metallic solid. Drude's model described properties of metals in terms of a gas of free electrons, and was the first microscopic model to explain empirical observations such as the Wiedemann–Franz law. However, despite the success of Drude's free electron model, it had one notable problem, in that it was unable to correctly explain the electronic contribution to the specific heat of metals, as well as the temperature dependence of resistivity at low temperatures.

In 1911, just three years after helium was first liquified, Onnes working at University of Leiden discovered superconductivity in mercury, when he observed the electrical resistivity in mercury to vanish when the temperature was lowered below a certain value. The phenomenon completely surprised the best theoretical physicists of the time, and it remained unexplained for several decades. Albert Einstein, in 1922, said regarding contemporary theories of superconductivity that “with our far-reaching ignorance of the quantum mechanics of composite systems we are very far from being able to compose a theory out of these vague ideas”