ELFT HÍRADÓ

[Andras Palyi <palyi AT mail.bme.hu>]

Dear Colleagues, 

Next Monday the BME Exotic Quantum Phases seminar continues with this online 
talk:

    Andreas Schnyder (Max Planck Institute for Solid State Research, 
Stuttgart)
    Symmetry-enforced band topologies in metals and magnets

online in Teams
Time: May 31, Monday, 14:15
Abstract: see below.

Teams link:
https://teams.microsoft.com/l/meetup-join/19%3a98c537f3ff3a433983cc04579e4603af%40thread.tacv2/1622198577856?context=%7b%22Tid%22%3a%226a3548ab-7570-4271-91a8-58da00697029%22%2c%22Oid%22%3a%22f8b27e90-dbca-4bb5-813c-d6415577ec35%22%7d
 
<https://teams.microsoft.com/l/meetup-join/19:98c537f3ff3a433983cc04579e4603af AT thread.tacv2/1622198577856?context={%22Tid%22:%226a3548ab-7570-4271-91a8-58da00697029%22,%22Oid%22:%22f8b27e90-dbca-4bb5-813c-d6415577ec35%22}>
 

Best regards,
Andras Palyi 

= = = 

In this talk, I will survey recent developments regarding the topological 
classification of symmetry-enforced band topologies in (semi)metals and 
magnets. These topological properties of the band structure are enforced to 
exist by symmetry alone, independent of the band dispersion, orbital content, 
and chemical composition of the material [1]. Hence, once the space group 
symmetries that enforce the desired band topologies have been identified, a 
suitable material can be found simply by browsing materials databases by 
space group numbers [2-4]. In this way, we have identified, among others 
[2-5], the topological materials ZrIrSn [2] and ferromagnetic MnSi [5], which 
will be discuss in detail.

The material ZrIrSn exhibits Weyl nodal lines near the Fermi energy, whose 
existence is guaranteed by a glide mirror symmetry. The topology of this 
nodal line is characterized by a quantized Pi-Berry phase, which leads to 
drumhead surface states. Ferromagnetic MnSi, on the other hand, has 
topological nodal planes on the BZ boundary, which are enforced by a 
combination of time-reversal with screw rotation symmetries. These nodal 
planes are sources of Berry flux, which is absorbed by single Weyl points at 
the center of the BZ. We discuss experimental consequences of these nodal 
planes in the surface spectra and de Haas-van Alphen measurements [5].

[1] Y. Zhao, A. Schnyder, Phys. Rev. B 94, 195109 (2016)
[2] J. Zhang, Y. Chan, C. Chiu, M. Vergniory, L. Schoop, A. Schnyder, Phys. 
Rev. Materials 2, 074201 (2018)
[3] Y. Chan, B. Kilic, M. Hirschmann, C. Chiu, L. Schoop, D. Joshi, A. 
Schnyder, Phys. Rev. Materials 3, 124204 (2019)
[4] M. Hirschmann, A. Leonhardt, B. Kilic, D. Fabini, A. Schnyder, 
arXiv:2102.04134
[5] M. Wilde, M. Dodenhöft, A. Niedermayr, A. Bauer, C. Pfleiderer, to appear 
in Nature