Topological Insulators - GDR Meso

Surface States of 3D Topological Insulators
• The Z2 topological order in the bulk
(band inversion induced by strong spin orbit)
• Robust edge (surface) states : Dirac fermions (odd number)
• First proposed candidate : Bi1-xSbx
Fu and Kane PRB 76 (2007)
«strong» topological insulator,
ν0 =1, not layered
• Second generation 3D Topological Insulators
Bi2Se3, Bi2Te3, Sb2Te3, ...
• Reference material : Bi2Se3
‣ single Dirac cone at the surface, stoichiometric, large band gap : 0.3 eV
• «Third generation» 3D Topological Insulators
‣ TlBiTe2, Bi2Te3 ·(GeTe)0.5
‣ strained HgTe : Ideal material ?
L. Molenkamp group, PRL (2011)
T. Meunier et L. Lévy : cf talk by C. Bouvier
How to probe experimentally these 3D Top. Insulators ?
‣ existence of surface states (Dirac fermions) :
‣ (spin resolved) ARPES
‣ STM
‣ transport ... problem : get rid of bulk contribution
mardi 3 janvier 12
Checkelsky et al., PRL. 103, 246601 (2009)
Zhang H. et al., Nat. Phys. 5, 438 (2009)
ARPES of topological insulator
First observation by D. Hsieh et al. (Z. Hasan group), Princeton/LBL, 2008.
This is later data on Bi2Se3 from the same group in 2009:
The states shown are in the “energy gap” of the bulk material--in general n