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Seminário de Matéria Condensada

Título:  Topological Anderson insulators

Data e horário: 25/05 quarta-feira às 11h
Local: sala 429 (torre nova)

Resumo: Insulating materials are ‘topological’ if their band structure
encapsulates a non-trivial topological index. While the bulk
properties of topological insulators are not remarkable (a fact that
has prevented their discovery for decades), their most striking
signature is the presence of conducting surface states — the
celebrated bulk/boundary correspondence of topological matter. How do
topological insulators respond to the inevitable presence of static
disorder? Given that, by definition, topological structures are
protected against ‘weak deformations’, a tentative answer might be:
not by much. In this talk, we will argue that the contrary is true and
that disorder takes an unexpectedly strong influence on the properties
of topological matter: in the bulk, even weak amounts of impurities
compromise the insulating band gaps crucial to our understanding of
topological matter. We will discuss how this band closure is
accompanied by the emergence of the topological Anderson insulator, a
material class characterised by distinct types of bulk quantum
critical phenomena, and highly universal surface properties. The talk
will start with a concise but self contained introduction to
topological insulators, first from a clean, then from a disordered
perspective. We will introduce the topological Anderson insulator and
explore its bulk and boundary properties. A number of concrete
ramifications of the presence of disorder, notably with regard to the
current search for Majorana fermions states in semiconductor quantum
wires will be addressed.