Abstract
Higher order topological insulators (HOTIs) are a new class of topological materials which host protected states at the corners or hinges of a crystal. HOTIs provide an intriguing alternative platform for helical and chiral edge states and Majorana modes, but there are very few known materials in this class. Recent studies have proposed Bi as a potential HOTI, however, its topological classification is not yet well accepted. In this work, we show that the (110) facets of Bi and BiSb alloys can be used to unequivocally establish the topology of these systems. Bi and Bi0.92Sb0.08 (110) films were grown on silicon substrates using molecular beam epitaxy and studied by scanning tunneling spectroscopy. The surfaces manifest rectangular islands which show localized hinge states on three out of the four edges, consistent with the theory for the HOTI phase. This establishes Bi and Bi0.92Sb0.08 as HOTIs, and raises questions about the topological classification of the full family of BixSb1−x alloys.
Highlights
Higher order topological insulators (HOTIs) are a new class of topological materials which host protected states at the corners or hinges of a crystal
While several groups have recently succeeded in observing HOTI phases in an electronic circuit, phononic, and photonic systems[7,8,9,10], the experimental realization and characterization of HOTIs in solid-state materials has proven more challenging
We propose that the observed edge states of an island on the surface can be ascribed to C^2 and time-reversal symmetry bulk crystal around the protected higher-order topology consistent with ref
Summary
Higher order topological insulators (HOTIs) are a new class of topological materials which host protected states at the corners or hinges of a crystal. The surfaces manifest rectangular islands which show localized hinge states on three out of the four edges, consistent with the theory for the HOTI phase This establishes Bi and Bi0.92Sb0.08 as HOTIs, and raises questions about the topological classification of the full family of BixSb1−x alloys. A recent study[1] ascribed the metallic edge modes to the manifestation of a bulk HOTI protected by crystalline and time-reversal symmetries. The confirmation of Bi as a HOTI would indicate that the low-energy bands of bismuth must have trivial time-reversal protected Z2 topology[1,18] This has implications for the topology of bulk Bi, which still remains controversial, and the family of Bi1−xSbx alloys
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
