Vendredi 06 décembre 2013 à 16h15
Auditoire Stueckelberg, Ecole de Physique

Bulk-edge duality for topological insulators

Gian Michele Graf, ETH Zürich

Topological insulators are materials which are conducting at their edges, though not in the bulk. Their Hamiltonian can not be deformed into those of ordinary insulators while retaining (fermionic) time-reversal invariance and the insulating property. After reviewing some of the reasons for the interest they recently raised, indices will be defined for insulators, telling apart the two types. We will do so for two-dimensional insulators: once based on the electronic bulk states, and once on the edge stases. We explain why the indices are equivalent (duality). The result requires only translation invariance of the material in the direction of the edge, but in the case of full translation invariance the bulk edge can be expressed in terms of Bloch states. (Joint work with M. Porta)