Ari Turner and Ashvin Vishwanath. “Beyond Band Insulators: Topology of Semi-metals and Interacting Phases.” arXiv preprint arXiv:1301.0330 (2013). – Part 1

Beyond Band Insulators: Topology of Semi-metals and Interacting Phases (Part 1)

This paper marks the beginning of the “interacting phase” of the journal club. The Qi and Zhang RMP marked the completion of the study of all the properties of topological phases in which the s- and p-orbitals gave rise to all the non-interacting topological phenomena. In other words, the s- and p-orbitals, which rarely exhibit strong electronic correlation effects, lie closest to the chemical potential and hence determine the most relevant electronic properties of the host material. It is obvious that the study of a broader list of topological phenomena requires parameters other than spin-orbit coupling as well.

The most accessible insulating phases with appreciable electronic correlations exist in a variety of Transition Metal Oxides (TMOs). Based on the location of transition metals in the periodic table it is easy to see that the d-orbitals lie closest to the chemical potential. The TMOs have already been studied for a wide range of interesting phases such as magnetism, Mott insulators, high-temperature superconductivity, etc. Adding another degree of freedom, namely spin-orbit coupling, appreciably expands the “phase space.” The first part of this paper reviews this so-called Weyl semi-metal (WSM) phase. Although the WSM phase can be theoretically treated as a non-interacting phase, time-reversal symmetry breaking due to magnetism can only arise from electronic correlations. At the time of writing of this paper, the WSM phase was not observed in the inversion symmetry breaking material with without correlations.

With the permission of the presenter, the slides for this journal club meeting can be found in the PDF file here. The PDF slides are only in the reading mode; they do not contain any animations. If you wish to get the original PowerPoint slides then please contact the presenter. If you notice any typos or scientific inaccuracies in the slides, I would be grateful if you could bring them to my attention by sending me an email.