Topological Insulators

Topological insulators exhibit surface states which are protected by the symmetry of the insulating bulk. They cannot be detroyed by local defects at the surface. We investigate weak topological insulators which provide conducting edge states at the surface. Additionally, we probe whether phase change materials (that can be switched between crystalline and amorphous on a ns time scale) are also topological insulators in their crystalline phase. Furthermore, we prepare interfaces which potentially host Majorana Fermions (Wikipedia). These investigations are related to quantum Hall systems which also contain topologically protected states.

Central goal is the imaging of topological properties on a local scale.

Methods

  • Angle-resolved photoemission spectroscopy (ARPES) with spin-resolution
  • Scanning tunneling microscopy (STM) and spectroscopy (STS)

Recent Projects

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Sub-Nanometer Wide Electron Channels in weak topological insulators (STS/ARPES)
Topological Band Inversion of the Phase Change Material Ge2Sb2Te5 (STM/STS/ARPES)
Spin polarized topological surface states on Sb2Te3(0001) (ARPES/STM/STS)
Landau level spectroscopy of the topological surface state of Sb2Te3 (STM/STS)
Tuning the Fermi energy to the Dirac point in the ternary topological insulator (Bi1-xSbx)2Te3 (ARPES)
Majorana excitations at the interface of superconductors and topological insulators (STS)