ELFT HÍRADÓ

[Zsolt Kovács <kovacs.zsolt AT ttk.elte.hu>]

ELTE Fizikai Intézet, Anyagfizikai Tanszék TANSZÉKI SZEMINÁRIUM
*2023. november 14.*, kedd *8:30*-kor az ELTE Pázmány Péter sétány 1/A 
alatti épületében, a 4.52 (Sas Elemér) teremben, vagy online: Teams-en 
az Anyagfizikai Tanszék [TTK] csoportban *Varjas Dániel *(IFW Dresden, 
Germany)*****Disordered topological phases in alloys, quasicrystals, and 
amorphous materials* Minden érdeklődőt szívesen látunk,külsős vendégeink 
ezen a linken 
<https://teams.microsoft.com/l/meetup-join/19%3aa75ae9289bfd4d4fbfb5b5c72892db6b%40thread.tacv2/1699517455203?context=%7b%22Tid%22%3a%22b366dbcd-4fc3-4451-82d2-e239564302c3%22%2c%22Oid%22%3a%2287fe0ca6-4d26-4ef4-b521-fc5cc13203cb%22%7d> 
is tudnak csatlakozni az előadáshoz Kovács Zsolt abstract: Topological phases of matter are distinguished by robust properties that
 are insensitive to perturbations. These include quantized responses,
perfectly conducting interfaces, and exactly zero energy modes, with
wide-ranging technological applications. Recent years saw the complete
classification of topological band structures, revealing an abundance of
 topological crystalline insulators. Many questions about the robustness
 of these phases to disorder are, however, still open. We develop new
theoretical and numerical methods based on local topological markers and
 effective momentum-space Hamiltonians to study topological phases in
disordered systems. As an example application, we tighten the critical
concentration for the topological phase transition of the experimentally
 relevant PbSnTe mirror Chern insulator alloy, using an ab initio
derived atomistic model. We also demonstrate the possibility of
higher-order topological materials beyond the existing classification
framework, protected by quasicrystalline symmetries. Finally we turn to
amorphous materials, topological phases of which are still uncharted,
even though it is a subset of materials of comparable size to crystals.
We introduce the topological Weaire-Thorpe class of models, whose
short-range properties allow us to analytically predict spectral gaps
and topological phase diagrams, which determine quantized observables
like circular dichroism, by introducing symmetry indicators for the
first time in an amorphous system.