Advanced Seminar SS 2018
"Spin-related Phenomena in Solids"
Mo. 14:00-15:00 h in the Seminar Room 202 of the II. Physikalisches Institut, University of Cologne.
The electron spin is not only the source of magnetic exchange and magnetic order in solids, it also influences a plethora of other condensed matter properties. In this advanced seminar we want to discuss a variety of spin-related phenomena which are currently in the focuse of modern condensed matter research. One aspect is the influence of spin-orbit coupling which couples the spin orientation of the electron to its orbital motion. In free atoms, this coupling causes the fine-structure splitting of the spectral lines and also determines the ground state term of a partially filled shell via the third Hund's rule. In solids, this "atomic effect" competes with the crystal electric field and/or the band formation. This may cause so-called topological insulators, which are insulating in the bulk but host metallic surface states, or so-called spin-liquid behaviour that is characterized by highly entangled groundstates with coontinuous excitation spectra. Magnetic frustration, that is the competition between different types of magnetic exchange couplings, can also induce spin-liquid behavior, in particular, when quantum fluctuations are enhanced as it is the case in 1- or 2-dimensional magnetic systems with small spin quantum numbers. For larger spins in 3-dimensional systems, magnetic frustration may cause long-range magnetic order with complexe spin structures that simultaneously break time and inversion symmetry. Such so-called multiferroic systems with coexisting magnetic and ferroelectric order are of strong potential interest for new types of data storage devices.
Within the seminar several spin-depentdent phenomena shall be introduced and discussed by the students. The seminar talks shall focus on the presentation of the experimental signatures of these phenomena in different materials. In addition, the experimental techniques used for their observation and an overview about the underlying theoretical concepts should be given.
Talks
| Date | Title | Tutor | Speaker | |
|---|---|---|---|---|
| 4.6. | Spin plasmons in topological insulators | M. Grüninger | L. Klaas |  pdf |
| 11.6. | Devices to address topological superconductivity | Y. Ando | Mengmeng Bai | pdf |
| 18.6. | Magnetic monopoles in spin ice | J. Hemberger | T. Leich | pdf |
| 25.6. | Kitaev spin liquids | P. van Loosdrecht | J. Wagner | |
| 2.7. | Complex spin textures at surfaces and their application for novel memory devices | T. Michely J. Fischer | R. Bernhard | pdf |
| 9.7. | Spin‐state transitions in cobaltates | T. Lorenz | C. Speckmann | pdf |
| 16.7. | Anomalous Hall effect in ferromagnetic oxide heterostructures | I. Lindfors-Vrejoiu | L. Wysocki | pdf |