Universität zu Köln

Wilfert, Stefan, Sessi, Paolo ORCID: 0000-0003-1261-0386, Wang, Zhiwei ORCID: 0000-0003-0182-2471, Schmidt, Henrik, Martinez-Velarte, M. Carmen, Lee, Seng Huat, San Hor, Yew, Otte, Alexander F., Ando, Yoichi ORCID: 0000-0002-3553-3355, Wu, Weida ORCID: 0000-0003-1691-6091 and Bode, Matthias ORCID: 0000-0001-7514-5560 (2018). Scanning tunneling spectroscopy investigations of superconducting-doped topological insulators: Experimental pitfalls and results. Phys. Rev. B, 98 (8). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2469-9969

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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 T-C = 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 E-D = -(118 +/- 1) meV and a Dirac velocity v(D) = (4.7 +/- 0.1) x 10(5) m/s. Tunneling spectra often show a superconducting gap, but temperature and field-dependent measurements show that both T(C )and mu H-0(C) 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.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Wilfert, Stefan UNSPECIFIED UNSPECIFIED UNSPECIFIED Sessi, Paolo UNSPECIFIED orcid.org/0000-0003-1261-0386 UNSPECIFIED Wang, Zhiwei UNSPECIFIED orcid.org/0000-0003-0182-2471 UNSPECIFIED Schmidt, Henrik UNSPECIFIED UNSPECIFIED UNSPECIFIED Martinez-Velarte, M. Carmen UNSPECIFIED UNSPECIFIED UNSPECIFIED Lee, Seng Huat UNSPECIFIED UNSPECIFIED UNSPECIFIED San Hor, Yew UNSPECIFIED UNSPECIFIED UNSPECIFIED Otte, Alexander F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ando, Yoichi UNSPECIFIED orcid.org/0000-0002-3553-3355 UNSPECIFIED Wu, Weida UNSPECIFIED orcid.org/0000-0003-1691-6091 UNSPECIFIED Bode, Matthias UNSPECIFIED orcid.org/0000-0001-7514-5560 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-176176
DOI:	10.1103/PhysRevB.98.085133
Journal or Publication Title:	Phys. Rev. B
Volume:	98
Number:	8
Date:	2018
Publisher:	AMER PHYSICAL SOC
Place of Publication:	COLLEGE PK
ISSN:	2469-9969
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics II
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SPIN; CUXBI2SE3; BREAKING; FERMIONS; STATES; FILMS; ORDER Multiple languages Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/17617