ESPCI web site
Jeudi 20 Juin 2013, 14h
Amphi Holweck, Esc C, 1ème etage
Strained HgTe Topological Insulator : Transport measurements & ARPES results
Olivier Crauste
Institue Néel, Grenoble
Topological Insulators (TI) are a new class of materials that have been
recently proved of great interest both theoretically and experimentally.
These systems are defined by an inversion of the band structure at the
time reversal symmetry point Γ. Intrinsically, they remain insulating in the bulk. The non-trivial properties arise at the interface with another topological class material, a normal insulator for example : the surface becomes metallic, with massless Dirac fermions and non dispersive transport. Due to its strong spin-orbit interaction, HgTe is a semi-metal with such a band structure inversion around the point Γ and is a very promising
strong Topological Insulator. In order to unveil its non-trivial
topological properties, HgTe samples are synthesized by Molecular Beam
Epitaxy methods by P. Ballet (CEA/Leti) with a uniform strain that opens
a gap. Angle-Resolved PhotoEmission Spectroscopy (ARPES), with its thin depth
sensitivity, is a dedicated technique to study the protected surface
states that occur at the interface between two systems of different
topological classes and has already given convincing results on Bi2Se3
Topological Insultator systems.
I will present our last results obtained by magneto-transport
measurements and the ARPES band structure acquired on the CASSIOPEE line at the SOLEIL synchrotron. These show a Dirac cone of the surface states which Dirac point lies just below the top of the Γ8 heavy hole band. This is confirmed by our theoretical simulation.