The invisible Majorana bound state at the helical edge Christoph Fleckenstein, Felix Keidel, Björn Trauzettel and Niccoló Traverso Ziani Eur. Phys. J. Special Topics, 227 12 (2018) 1377-1386 Published online: 17 September 2018 DOI: 10.1140/epjst/e2018-800093-5