Magneto-transport studies of strained HgTe topological insulators

September 14 2011
Types d’événements
Séminaire SPEC
Laurent Lévy
SPEC Salle Itzykson, Bât.774
14/09/2011
from 11:15

Topological insulators is a class of material conducting on the surface and not in the bulk. In HgTe a P band is inverted with respect to an S band (negative gap): this change this semiconductor for insulator to topological insulator. A bandgap can be opened by growing it on a substrate with a lattice mismatch which strains homogenously the material. The conducting surface states lie partly in this bandbap.
Using a gated Hall device we have
– done the spectrocopy of the Dirac states in weak field magneto-transport, placing the Dirac point with a 100 microvolt accuracy
– Observed antilocalization correction to the conductivity, typical of Dirac Fermions
– analyzed the dependence of the chemical potential with density using Shubnikov deHaas frequencies.
– Observed two sets of Hall plateaus: a half odd integer serie, consistent with a single Dirac cone and an integer serie which is unexpected. An insulating phase appears at high field.

The talk will cover only a fraction of this material for pedagogical reasons.

Institut Néel (CNRS), Grenoble