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Higher-order topological insulators - Titus Neupert

Université de Zurich

LPS – salle 208a

Three-dimensional topological (crystalline) insulators are materials with an insulating bulk, but conducting surface states which are topologically protected by time-reversal (or spatial) symmetries. I will present an extension of the notion of three-dimensional topological insulators to systems that host no gapless surface states, but exhibit topologically protected gapless hinge states. Their topological character is protected by spatio-temporal symmetries, of which we present two cases : (1) Chiral higher-order topological insulators with hinge states that are chiral modes. (2) Helical higher-order topological insulators protected by time-reversal and spatial symmetries. Their hinge states come in Kramers pairs akin to the edge states of the quantum spin Hall effect. I will discuss the topological invariants for both cases as well as material candidates.


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