Probing Edge State Conductance in Ultra‐Thin Topological Insulator Films

Advanced Quantum Technologies, vol. 5

Abstract

Abstract Quantum spin Hall (QSH) insulators have unique electronic properties, comprising a band gap in their 2D interior and 1D spin‐polarized edge states in which current flows ballistically. In scanning tunneling microscopy (STM), the edge states manifest themselves as an enhanced local density of states (LDOS). However, there is a significant research gap between the observation of edge states in nanoscale spectroscopy, and the detection of ballistic transport in edge channels which typically relies on transport experiments with microscale lithographic contacts. Here, few‐layer films of the 3D topological insulator (Bi x Sb) 2 Te 3 are studied, for which a topological transition to a 2D topological QSH insulator phase has been proposed. Indeed, an edge state in the LDOS is observed within the band gap. Yet, in nanoscale transport experiments with a four‐tip STM, two‐quintuple‐layer films do not exhibit a ballistic conductance in the edge channels and thus no QSH edge states. This demonstrates that the detection of edge states in spectroscopy can be misleading with regard to the identification of a QSH phase. In contrast, nanoscale multi‐tip transport experiments are a robust method for effectively pinpointing ballistic edge channels, as opposed to trivial edge states, in quantum materials.

Authors 11

1. Arthur Leis Aachen Experimentalphysik IV A

   RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Experimentalphysik IV A RWTH Aachen University Otto‐Blumenthal‐Straße 52074 Aachen Germany

   Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

   Peter Grünberg Institut (PGI‐3) Forschungszentrum Jülich 52425 Jülich Germany

2. Michael Schleenvoigt

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

   Peter Grünberg Institut (PGI‐9) Forschungszentrum Jülich 52425 Jülich Germany

3. Kristof Moors

   Forschungszentrum Jülich

   Affiliation as printed

   Peter Grünberg Institut (PGI‐9) Forschungszentrum Jülich 52425 Jülich Germany

4. Helmut Soltner

   Forschungszentrum Jülich

   Affiliation as printed

   Zentralinstitut für Engineering Elektronik und Analytik (ZEA‐1) Forschungszentrum Jülich 52425 Jülich Germany

5. Vasily Cherepanov

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

   Peter Grünberg Institut (PGI‐3) Forschungszentrum Jülich 52425 Jülich Germany

6. Peter Schüffelgen

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

   Peter Grünberg Institut (PGI‐9) Forschungszentrum Jülich 52425 Jülich Germany

7. Gregor Mußler

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

   Peter Grünberg Institut (PGI‐9) Forschungszentrum Jülich 52425 Jülich Germany

8. Detlev Grützmacher

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

   Peter Grünberg Institut (PGI‐9) Forschungszentrum Jülich 52425 Jülich Germany

9. Bert Voigtländer corresponding Aachen Experimentalphysik IV A

   RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Experimentalphysik IV A RWTH Aachen University Otto‐Blumenthal‐Straße 52074 Aachen Germany

   Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

   Peter Grünberg Institut (PGI‐3) Forschungszentrum Jülich 52425 Jülich Germany

10. Felix Lüpke

    Forschungszentrum Jülich · Jülich Aachen Research Alliance

    Affiliation as printed

    Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

    Peter Grünberg Institut (PGI‐3) Forschungszentrum Jülich 52425 Jülich Germany

11. Frank Stefan Tautz Aachen Experimentalphysik IV A

    RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

    Affiliation as printed

    Experimentalphysik IV A RWTH Aachen University Otto‐Blumenthal‐Straße 52074 Aachen Germany

    Jülich Aachen Research Alliance (JARA) Fundamentals of Future Information Technology 52425 Jülich Germany

    Peter Grünberg Institut (PGI‐3) Forschungszentrum Jülich 52425 Jülich Germany