Universität zu Köln

Knispel, T., Jolie, W., Borgwardt, N., Lux, J., Wang, Zhiwei ORCID: 0000-0003-0182-2471, Ando, Yoichi ORCID: 0000-0002-3553-3355, Rosch, A., Michely, T. and Grueninger, M. (2017). Charge puddles in the bulk and on the surface of the topological insulator BiSbTeSe2 studied by scanning tunneling microscopy and optical spectroscopy. Phys. Rev. B, 96 (19). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2469-9969

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Abstract

The topological insulator BiSbTeSe2 corresponds to a compensated semiconductor in which strong Coulomb disorder gives rise to the formation of charge puddles, i.e., local accumulations of charge carriers, both in the bulk and on the surface. Bulk puddles are formed if the fluctuations of the Coulomb potential are as large as half of the band gap. The gapless surface, in contrast, is sensitive to small fluctuations but the potential is strongly suppressed due to the additional screening channel provided by metallic surface carriers. To study the quantitative relationship between the properties of bulk puddles and surface puddles, we performed infrared transmittance measurements as well as scanning tunneling microscopy measurements on the same sample of BiSbTeSe2, which is close to perfect compensation. At 5.5 K, we find surface potential fluctuations occurring on a length scale r(s) = 40-50 nm with amplitude Gamma = 8-14 meV, which is much smaller than in the bulk, where optical measurements detect the formation of bulk puddles. In this nominally undoped compound, the value of Gamma is smaller than expected for pure screening by surface carriers, and we argue that this arises most likely from a cooperative effect of bulk screening and surface screening.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Knispel, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Jolie, W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Borgwardt, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lux, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wang, Zhiwei UNSPECIFIED orcid.org/0000-0003-0182-2471 UNSPECIFIED Ando, Yoichi UNSPECIFIED orcid.org/0000-0002-3553-3355 UNSPECIFIED Rosch, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Michely, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Grueninger, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-211171
DOI:	10.1103/PhysRevB.96.195135
Journal or Publication Title:	Phys. Rev. B
Volume:	96
Number:	19
Date:	2017
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 Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/21117