MPhys Student project for 2019/20

Simulation of spin dynamics for Dirac and Weyl magnons

This is a combined theory/computational project to simulate/visualize the spin oscillations in interacting spin systems, as part of the broader research effort in the quantum magnetism group to explore experimentally using inelastic neutron scattering the spin dynamics of magnets with strong spin-orbit coupling. Of particular interest are magnetic materials that can support linear touching points between spin-wave bands, analogous to the electron band touchings in a single honeycomb layer of carbon atoms (graphene) where electrons behave like Dirac particles with a relativistic dispersion (linear in momentum) near the touching points. We are interested in magnetic analogues of such physics, where dispersive bands of collective spin oscillations (spin waves) can display touching points, leading to Dirac (in two dimensions) and Weyl magnons (in three dimensions) [1]. The aim of the project is to develop computer code to simulate/visualize how the spins oscillate near the band-touching points, and understand the effects of spin-orbit coupling and externally applied magnetic fields, which can shift the bands and in certain circumstances open gaps. The project will require theoretical derivations of „normal modes” of spin oscillations and coding to create movies of the time-evolution of the spins. Support can be offered for coding in matlab. The project will benefit from existing numerical code to determine the eigevector of normal spin-wave modes for a multi-sublattice system.

[1] S.A. Owerre, Journal of Physics: Condensed Matter 28, 386001 (2016). https://iopscience.iop.org/article/10.1088/0953-8984/28/38/386001/meta

This project would require the ability to learn independently from books and papers and a very keen interest and experience in programming (suitable for 1 student taking the C6 Theory or C3 CMP option).

Supervisor: Prof Radu Coldea radu.coldea@physics.ox.ac.uk