# Gapped boundary phases of topological insulators via weak coupling

@article{Seiberg2016GappedBP, title={Gapped boundary phases of topological insulators via weak coupling}, author={Nathan Seiberg and Edward Witten}, journal={Progress of Theoretical and Experimental Physics}, year={2016}, volume={2016} }

The standard boundary state of a topological insulator in 3 + 1 dimensions has gapless charged fermions. We present model systems that reproduce this standard gapless boundary state in one phase, but also have gapped phases with topological order. Our models are weakly coupled and all the dynamics is explicit. We rederive some known boundary states of topological insulators and construct new ones. Consistency with the standard spin/charge relation of condensed matter physics places a nontrivial…

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