Universität zu Köln

Bagchi, Mahasweta, Brede, Jens ORCID: 0000-0002-4946-8160 and Ando, Yoichi ORCID: 0000-0002-3553-3355 (2022). Observability of superconductivity in Sr-doped Bi2Se3 at the surface using scanning tunneling microscope. Phys. Rev. Mater., 6 (3). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2475-9953

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Abstract

The superconducting materials family of doped Bi2Se3 remains intensively studied in the field of condensed matter physics due to strong experimental evidence for topologically nontrivial superconductivity in the bulk. However, at the surface of these materials, even the observation of superconductivity itself is still controversial. We use scanning tunneling microscopy (STM) down to 0.4 K to show that on the surface of bulk superconducting SrxBi2Se3, no gap in the density of states is observed around the Fermi energy as long as clean metallic probe tips are used. Nevertheless, using scanning electron microscopy and energy-dispersive x-ray analysis, we find that micrometer-sized flakes of SrxBi2Se3 are easily transferred from the sample onto the STM probe tip and that such flakes consistently show a superconducting gap in the density of states. We argue that the superconductivity in SrxBi2Se3 crystals does not extend to the surface when the topological surface state (TSS) is intact, but in microflakes, the TSS has been destroyed due to strain and allows the superconductivity to extend to the surface. To understand this phenomenon, we propose that the local electric field, always found in electron-doped Bi2Se3 in the presence of the TSS due to an intrinsic upward band bending, works against superconductivity at the surface.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Bagchi, Mahasweta UNSPECIFIED UNSPECIFIED UNSPECIFIED Brede, Jens UNSPECIFIED orcid.org/0000-0002-4946-8160 UNSPECIFIED Ando, Yoichi UNSPECIFIED orcid.org/0000-0002-3553-3355 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-661431
DOI:	10.1103/PhysRevMaterials.6.034201
Journal or Publication Title:	Phys. Rev. Mater.
Volume:	6
Number:	3
Date:	2022
Publisher:	AMER PHYSICAL SOC
Place of Publication:	COLLEGE PK
ISSN:	2475-9953
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language Materials Science, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/66143