# Tilman Enss | Teaching — Condensed Matter Theory 2

as of April 2020

## Condensed Matter Theory 2

#### Summer term 2020

This course introduces the concepts and methods of modern condensed matter theory. We will discuss metals, superconductors, magnetism and quantum liquids. We will introduce Green's functions and the diagrammatic technique, effective low-energy models, classical and quantum phase transitions. The exercises practise the different theoretical techniques and also show how to compute experimental observables.

#### Contents

- Introduction
- Green's functions and perturbation theory
- Green's functions
- Coherent states
- Path integrals
- Wick's theorem and perturbation theory

- Metals
- Jellium model
- Charge excitations and screening
- Phonons

- Superconductivity
- Fröhlich model
- BCS theory of superconductivity
- Hubbard model and high-Tc superconductors

- Magnetism
- Classical magnets (Ising, XY, Heisenberg) and phase transitions
- Quantum magnets (transverse Ising) and quantum phase transitions

- Quantum liquids
- Landau Fermi liquid theory
- Luttinger liquids

#### Dates and Location

Lecture Monday 11.15-13.00h, Philosophenweg 12, kHS [LSF]

and Wednesday 11.15-13.00h, Philosophenweg 12, kHS.

Exercise Tuesday 09.15-11.00h, Philosophenweg 19, seminar room.

The lecture starts online on April 20.

Please register for the course and then follow the curriculum on the course website.

#### Prerequisites

- Condensed Matter Theory 1 (in particular second quantization, tight binding lattice models and Hartree-Fock, as summarized in my CMT1 primer)
- Quantum Mechanics (PTP4)
- Theoretical Statistical Physics (MKTP1)

#### Literature

Literature will be announced in the first lecture. Some recommended books:

- Ashcroft and Mermin, Solid State Physics
- Altland and Simons, Condensed Matter Field Theory
- Fetter and Walecka, Quantum Theory of Many-Particle Systems
- Negele and Orland, Quantum Many-Particle Systems
- Tinkham, Introduction to Superconductivity