The framework developed in this course for understanding the properties of condensed matter is based upon the approximation of non-interacting (or weakly interacting) particles. At the simplest level, it is the Pauli exclusion principle alone that determines all the properties of solids. Together with the concept of crystalline order, Bose-Einstein statistics for excitations of the lattice, and the effects of weak interactions, this is the basis for understanding electrical, optical, thermal, and mechanical properties of solids. The nature of electrons near the Fermi surface in metals and the electrical properties of semiconductors will be the primary examples of the applications of these ideas. Experiments which directly demonstrate key properties will be discussed.
It is also essential to realize that one must go beyond independent-particle pictures in order to understand many of the phenomena of condensed matter, such as magnetism, superconductivity, and phase transitions, which arise from cooperative "many-body" behavior. Such cooperative effects in condensed matter are not only important in themselves but also are paradigms for understanding similar phenomena in many fields of science. In the latter part of the course, we will lay some of the groundwork for these ideas and their consequences.