Lecture 1: Background and Scope Introduction In this lecture you are given an overview of what the entire course is all about. It contains information about the relevant background knowledge required, as well as the scope of the course and the tools required to complete it successfully. The properties that are common to all solids as well as the ones that can be used to differentiate among them are also specified. 1.1. Macroscopic and Microscopic Properties The ‘Bulk or Macroscopic’ properties of solids, e.g. their Electrical and Thermal Conductivity, Mechanical Strength, Heat Capacity, etc., are determined by the (collective) behaviour of the ‘submicroscopic’ particles that make up the solids. These particles may be atoms, ions or molecules, and they are so many (~ 1023) in every solid material. In metals the electrons in the outermost shells of the atoms are loosely bound (to the atoms) – these are called valence electrons - therefore they move easily within the metals, carrying electricity and heat from one point to another. This is why metals are very good conductors, i.e. presence of valence electrons (Microscopic property) in metals manifests into high conductivity (bulk or macroscopic property). You will come across more examples of such relationship between macroscopic properties of solids and the microscopic properties of the atoms. Solids are made of many submicroscopic particles (atoms, ions, and molecules). The interactions among these particles determine the overall (macroscopic) properties of the solids.
21.2. Length and Energy Scales in Solid State Physics In Solid State Physics we normally encounter energies below Electron Volt (eV), whereas in Nuclear Physics, they deal with energies in the order of MeV, and in Particle Physics they talk about Giga Electron Volt (GeV) or more. Also, unlike in nuclear and particle physics, the length scale of interest in solid-state physics is >> 10-10m, i.e. much greater than what you will encounter in Nuclear and Particle Physics, but they are much smaller than what is encountered in Astrophysics and Cosmology where the force of gravity becomes very important. 1.3. Theoretical Tools Required in the Study of Solid State Physics In order to understand the content of this course, we shall make use of our knowledge in the other subjects, especially Mathematics, Introductory Quantum Physics, and Statistical Mechanics. Therefore we may digress now and then to update ourselves with the relevant tools from these subject areas whenever the needs arise. 1.4. Experimental Techniques Used in Probing Solids In the course of our discussion we shall explore some of the experimental techniques that are used by Experimental Physicists to probe matter and determine their quantitative properties, such as Mechanical Strength, Conductivity, Heat Capacity, etc., all of which are strongly associated with the arrangement of, and the interaction among atoms or ions that form the building blocks. The following are examples of the relevant experimental techniques: •Scattering: We can bombard a solid sample with radiation (e.g. neutrons or X-