# Boundary-obstructed topological phases

@article{Khalaf2019BoundaryobstructedTP, title={Boundary-obstructed topological phases}, author={Eslam Khalaf and Wladimir A. Benalcazar and Taylor L. Hughes and Raquel Queiroz}, journal={arXiv: Mesoscale and Nanoscale Physics}, year={2019} }

Symmetry protected topological (SPT) phases are gapped phases of matter that cannot be deformed to a trivial phase without breaking the symmetry or closing the bulk gap. Here, we introduce a new notion of a topological obstruction that is not captured by bulk energy gap closings in periodic boundary conditions. More specifically, we say two bulk Hamiltonians belong to distinct boundary obstructed topological `phases' (BOTPs) if they can be deformed to each other on a system with periodic…

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