Theory of Frustrated Magnetism

Frustrated Magnetism is one of the most active research area of modern condensed matter physics. Frustration refers to a situation where the contributions to the potential energy of a many-many body system cannot be simultaneously minimized, a prime example being a antiferromagnetic Ising model on a triangular lattice. Frustration is the source of many novel phases - in particular novel forms of disorder - and exciting phenomena connected to them, such as quantum number fractionalization. Frustrated magnets can e.g. display spin-liquid phases, with a deep connection to topological states of matter.

The lecture will give an introduction to the field, primarily from a theoretical and conceptual perspective. It will cover general ideas, concrete models for frustrated magnets, theoretical methods such as spin-wave theory, parton constructions, and gauge fields, as well as advanced topics. Relevant experimental observations will be discussed as well.

The lecture is suitable for Master students and PhD students, as well as for Bachelor students who are familiar with second quantization. Basic knowledge in many-particle theory (Green's functions, mean-field theory, diagrammatics) is helpful but not required.