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Quentin Marsal presents

 Topological phases in amorphous materials

Tuesday,  December 13th 2022 at 14:00

Seminar room – Building A – CNRS

The defence will be in French.

Link visio : https://univ-grenoble-alpes-fr.zoom.us/j/97884129323?pwd=RXN2UkhjS0JsbXluMy9hbXY0U2ExQT09

Meeting ID: 978 8412 9323
Passcode: 75982

 

Abstract:

Amorphous solids remain outside of the classification and systematic discovery of new topological materials, partially due to the lack of realistic models that are analytically tractable. Nevertheless, recent experiments have shown that topological boundary states exist in amorphous systems.

We introduce the topological Weaire-Thorpe class of models, which are defined on amorphous lattices with fixed coordination number, a realistic feature of covalently bonded amorphous solids. Our lattices have only structural disorder, meaning that all the sites are exactly the same, but bound together in a disordered way. As a consequence, local symmetries play a central role and can be used to compute analytically topological phase diagrams, introducing symmetry indicators for the first time in amorphous systems.The lack of translational invariance complicates the interpretation of angular-resolved photoemission spectroscopy (ARPES) spectra: the momentum of the photo-emitted electrons is not a proper quantum number anymore for the eigenstates of the system. To understand amorphous ARPES spectra, we compute the spectral function of an amorphous system. Our results indicate that amorphous systems can display sharp ARPES spectra, allowing experiments to identify their topological nature, even in the absence of a well defined crystal momentum.

 

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