title: Determination of the local structure of CsBi4-xPbxTe6(x = 0, 0.5) by X-ray absorption spectroscopy.
abstract: We have studied the local structure and valence electronic unoccupied states of thermoelectric CsBi4Te6and superconducting CsBi3.5Pb0.5Te6(Tc∼ 3 K) by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) measurements. The Bi-L3edge EXAFS reveals wide Bi-Te distance distribution for both compounds indicating complex atomic arrangements in the studied system. The mean square relative displacements (MSRDs) of the Bi-Te bond distances appear largely increased in Pb substituted system due to larger overall local disorder, however, one of the Bi-Te bonds shows a reduced disorder. On the other hand, the Bi-L3edge XANES is hardly affected by Pb substitution while the Te-L1edge XANES reveals increased density of unoccupied Te 5p states. This suggests that the carriers introduced by the Pb substitution in CsBi4-xPbxTe6preferentially goes on Te sites. Similarly, the Cs-L3edge XANES also shows small changes due to Pb-substitution and reduced local disorder indicated by the reduced width of the Cs-L3edge white line. We have also shown that the X-ray photoemission spectroscopy (XPS) measurements on various electronic core levels are in a qualitative agreement with the XANES results. These findings are consistent with carrier doping and a reduced disorder in one direction to be likely factors to drive the thermoelectric CsBi4Te6into a bulk superconductor by Pb-substitution in CsBi4-xPbxTe6.
authors.affiliation: Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan. wakita@cc.okayama-u.ac.jp.
authors.forename: Takanori
authors.initials: T
authors.lastname: Wakita
authors.affiliation: Dipartimento di Fisica, Sapienza Università degli Studi di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy and Center for Life NanoScience@Sapienza, Istituto Italiano di Tecnologia, V. le Regina Elena 291, 00161 Roma, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Paris
authors.affiliation: Department of Applied Physics, Waseda University, Tokyo 169-8555, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizokawa
authors.affiliation: Dipartimento di Fisica, Sapienza Università degli Studi di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy and Department of Physics, Recep Tayyip Erdogan University, 53100 Rize, Turkey.
authors.forename: Muammer Yasin
authors.initials: MY
authors.lastname: Hacisalihoglu
authors.affiliation: Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan. wakita@cc.okayama-u.ac.jp.
authors.forename: Kensei
authors.initials: K
authors.lastname: Terashima
authors.affiliation: Research and Utilization Division, Japan Synchrotron Radiation Research Institute, Kouto, Hyogo 679-5148, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okazaki
authors.affiliation: Observatoire des Sciences de l'Univers de Grenoble (OSUG), UMR CNRS 832, Universitè Grenoble-Alpes, 38041 Grenoble Cedex 9, France and BM30B/CRG-FAME, ESRF, Polygone Scientifique Louis Nèel, 71 avenue des Martyrs, 38000 Grenoble, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Proux
authors.affiliation: Observatoire des Sciences de l'Univers de Grenoble (OSUG), UMR CNRS 832, Universitè Grenoble-Alpes, 38041 Grenoble Cedex 9, France and BM30B/CRG-FAME, ESRF, Polygone Scientifique Louis Nèel, 71 avenue des Martyrs, 38000 Grenoble, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Kieffer
authors.affiliation: Observatoire des Sciences de l'Univers de Grenoble (OSUG), UMR CNRS 832, Universitè Grenoble-Alpes, 38041 Grenoble Cedex 9, France and BM30B/CRG-FAME, ESRF, Polygone Scientifique Louis Nèel, 71 avenue des Martyrs, 38000 Grenoble, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Lahera
authors.affiliation: Observatoire des Sciences de l'Univers de Grenoble (OSUG), UMR CNRS 832, Universitè Grenoble-Alpes, 38041 Grenoble Cedex 9, France and BM30B/CRG-FAME, ESRF, Polygone Scientifique Louis Nèel, 71 avenue des Martyrs, 38000 Grenoble, France.
authors.forename: William
authors.initials: W
authors.lastname: Del Net
authors.affiliation: Elettra-Sincrotrone Trieste, Strada Statale 16, Km 163.5, Bassovizza, Trieste, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Olivi
authors.affiliation: National Institute for Materials Science, Sengen, Tsukuba 305-0047, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Takano
authors.affiliation: Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan. wakita@cc.okayama-u.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Muraoka
authors.affiliation: Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan. wakita@cc.okayama-u.ac.jp.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Yokoya
authors.affiliation: Dipartimento di Fisica, Sapienza Università degli Studi di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy.
authors.forename: Naurang L
authors.initials: NL
authors.lastname: Saini