Speaker
Mr
Stefan Muff
(Paul Scherrer Institut)
Description
We identify the multi-layered compound GeBi_(4-x)Sb_xTe_7 to be a topological insulator with a freestanding Dirac point, slightly above the valence band maximum, using angle-resolved photoemission spectroscopy (ARPES) measurements. The spin polarization satisfies the time reversal symmetry of the surface states, visible in spin-resolved ARPES. For increasing Sb content in GeBi_(4-x)Sb_xTe_7 we observe a transition from n- to p-type in bulk sensitive Seebeck coefficient measurements at a doping of x=0.6. In surface sensitive ARPES measurements a rigid band shift is observed with Sb doping, accompanied by a movement of the Dirac point towards the Fermi level. Between x=0.8 and x=1 the Fermi level crosses the band gap, changing the surface transport regime. This difference of the n- to p-type transition between the surface region and the bulk is caused by band bending effects which are also responsible for a non-coexistence of insulating phases in the bulk and in the near surface region.
Primary author
Mr
Stefan Muff
(Paul Scherrer Institut)
Co-authors
Prof.
Andreas Schilling
(University of Zurich)
Dr
Bartosz Slomski
(Paul Scherrer Institut)
Mr
Fabian von Rohr
(University of Zurich)
Mr
Gabriel Landolt
(Paul Scherrer Institut)
Dr
Hugo Dil
(Paul Scherrer Institut)
Prof.
Jürg Osterwalder
(University of Zurich)
Prof.
Robert J. Cava
(Princeton University)
