Scanning tunneling spectroscopy investigations of superconducting-doped topological insulators: Experimental pitfalls and results

Stefan Wilfert, Paolo Sessi, Zhiwei Wang, Henrik Schmidt, M. Carmen Martínez-Velarte, Seng Huat Lee, Yew San Hor, Alexander F. Otte, Yoichi Ando, Weida Wu, Matthias Bode

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Recently, the doping of topological insulators has attracted significant interest as a potential route towards topological superconductivity. Because many experimental techniques lack sufficient surface sensitivity, however, definite proof of the coexistence of topological surface states and surface superconductivity is still outstanding. Here we report on highly surface sensitive scanning tunneling microscopy and spectroscopy experiments performed on Tl-doped Bi2Te3, a three-dimensional topological insulator which becomes superconducting in the bulk at TC=2.3 K. Landau level spectroscopy as well as quasiparticle interference mapping clearly demonstrated the presence of a topological surface state with a Dirac point energy ED=-(118±1) meV and a Dirac velocity vD=(4.7±0.1)×105 m/s. Tunneling spectra often show a superconducting gap, but temperature- and field-dependent measurements show that both TC and μ0HC strongly deviate from the corresponding bulk values. Furthermore, in spite of a critical field value which clearly points to type-II superconductivity, no Abrikosov lattice could be observed. Experiments performed on normal-metallic Ag(111) prove that the gapped spectrum is caused only by superconducting tips, probably caused by a gentle crash with the sample surface during approach. Nearly identical results were found for the intrinsically n-type compound Nb-doped Bi2Se3. Our results suggest that the superconductivity in superconducting-doped V-VI topological insulators does not extend to the surface where the topological surface state is located.

Original languageEnglish (US)
Article number085133
JournalPhysical Review B
Volume98
Issue number8
DOIs
StatePublished - Aug 20 2018

Fingerprint

Superconductivity
insulators
Spectroscopy
Scanning
Surface states
scanning
spectroscopy
superconductivity
Scanning tunneling microscopy
crashes
Experiments
Doping (additives)
scanning tunneling microscopy
routes
interference
Temperature

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Wilfert, Stefan ; Sessi, Paolo ; Wang, Zhiwei ; Schmidt, Henrik ; Martínez-Velarte, M. Carmen ; Lee, Seng Huat ; Hor, Yew San ; Otte, Alexander F. ; Ando, Yoichi ; Wu, Weida ; Bode, Matthias. / Scanning tunneling spectroscopy investigations of superconducting-doped topological insulators : Experimental pitfalls and results. In: Physical Review B. 2018 ; Vol. 98, No. 8.
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abstract = "Recently, the doping of topological insulators has attracted significant interest as a potential route towards topological superconductivity. Because many experimental techniques lack sufficient surface sensitivity, however, definite proof of the coexistence of topological surface states and surface superconductivity is still outstanding. Here we report on highly surface sensitive scanning tunneling microscopy and spectroscopy experiments performed on Tl-doped Bi2Te3, a three-dimensional topological insulator which becomes superconducting in the bulk at TC=2.3 K. Landau level spectroscopy as well as quasiparticle interference mapping clearly demonstrated the presence of a topological surface state with a Dirac point energy ED=-(118±1) meV and a Dirac velocity vD=(4.7±0.1)×105 m/s. Tunneling spectra often show a superconducting gap, but temperature- and field-dependent measurements show that both TC and μ0HC strongly deviate from the corresponding bulk values. Furthermore, in spite of a critical field value which clearly points to type-II superconductivity, no Abrikosov lattice could be observed. Experiments performed on normal-metallic Ag(111) prove that the gapped spectrum is caused only by superconducting tips, probably caused by a gentle crash with the sample surface during approach. Nearly identical results were found for the intrinsically n-type compound Nb-doped Bi2Se3. Our results suggest that the superconductivity in superconducting-doped V-VI topological insulators does not extend to the surface where the topological surface state is located.",
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Wilfert, S, Sessi, P, Wang, Z, Schmidt, H, Martínez-Velarte, MC, Lee, SH, Hor, YS, Otte, AF, Ando, Y, Wu, W & Bode, M 2018, 'Scanning tunneling spectroscopy investigations of superconducting-doped topological insulators: Experimental pitfalls and results', Physical Review B, vol. 98, no. 8, 085133. https://doi.org/10.1103/PhysRevB.98.085133

Scanning tunneling spectroscopy investigations of superconducting-doped topological insulators : Experimental pitfalls and results. / Wilfert, Stefan; Sessi, Paolo; Wang, Zhiwei; Schmidt, Henrik; Martínez-Velarte, M. Carmen; Lee, Seng Huat; Hor, Yew San; Otte, Alexander F.; Ando, Yoichi; Wu, Weida; Bode, Matthias.

In: Physical Review B, Vol. 98, No. 8, 085133, 20.08.2018.

Research output: Contribution to journalArticle

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T1 - Scanning tunneling spectroscopy investigations of superconducting-doped topological insulators

T2 - Experimental pitfalls and results

AU - Wilfert, Stefan

AU - Sessi, Paolo

AU - Wang, Zhiwei

AU - Schmidt, Henrik

AU - Martínez-Velarte, M. Carmen

AU - Lee, Seng Huat

AU - Hor, Yew San

AU - Otte, Alexander F.

AU - Ando, Yoichi

AU - Wu, Weida

AU - Bode, Matthias

PY - 2018/8/20

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