RKKY Interactions on Dirac Surfaces by Herbert A Fertig
International Centre for Theoretical Sciences via YouTube
Overview
Syllabus
RKKY Interactions on Dirac Surfaces
Outline
Effective spin-spin interaction
Another completely equivalent approach: second order perturbation theory
RKKY Interactions in Graphene: A Paradigms for Dirac Surfaces
3. Electron wavefunctions are helical
4. Different possible locations for spin impurities: sd exchange coupling to multiple sites possible
So AA response is different than AB response
Strong local antiferromagnetic correlations from single particle physics
Numerical check: graphene sheet with periodic boundary conditions nanotube
Can we induce ferromagnetism in graphene? Need to break symmetry between sublattices. One way: use strain!
Problem: Breakdown of second order perturbations theory
Hilbert Space of states in LLL: M angular momentum states
Relative angle
Remaining Landau levels handled by perturbation theory:
Mean-field theory for RKKY interactions in strained graphene: Pairwise RKKY interaction = LLL nonperturbative part + 2nd order perturbative part
Net Moment
Dirac Surfaces on Topological Insulators
Topological crystalline insulators TCI
In topological regime....For 1 11 surface: Dirac points present at I and M 3 of these points
Slab geometry:total free energy computed for different orientations
Many thanks to ....
Summary
Q&A
Taught by
International Centre for Theoretical Sciences