While much of the physics you have studied to date has been about taking things apart to find the fundamental laws and particles that underpin the universe, condensed matter physics is about putting matter back together again. A key theme will be the idea of the emergence – that to understand complex matter we need to understand the elementary excitations and these are usually different from the bare ingredients of solids (atoms with their associated electrons and nuclei). Emergent excitations include phonons as quantized lattice vibrations and the electron quasiparticle in the metallic state. The course will build on ideas covered in year two and apply many of the concepts of quantum mechanics and statistical physics in year 3. We will be particularly concerned with the affect of periodicity on the properties of waves in crystals (which, by virtue of wave-particle duality, will govern particles too). We will see how to use these properties to measure structure (via scattering experiments), to understand the process of transport in metals, to control properties (via semiconductor doping) and to see the role of Coulomb repulsion and Pauli exclusion in generating magnetism.

By the end of the module, the student should be able to:

• From a normal mode analysis, be able to characterize the acoustic and optic branches of a phonon dispersion (and relate this to observables like specific heat).
• See how quantized phonons emerge from a normal mode analysis.
• Determine Brillouin zones for periodic crystals and to relate this to bandstructures via nearly free and tight binding approaches.
• Calculate thermo-electric transport coefficients from a Boltzmann equation in the relaxation time approximation.
• Compute the doping concentration in semiconductors as a function of temperature for intrinsic semiconductors and understand how doping changes this.
• Understand the working of a semiconductor device.
• Use quantitatively the ideas of interactions and Pauli exclusions to account for ferromagnetism and antiferromagnetism.