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Unusual phonon density of states and response to the superconducting transition in the In-doped topological crystalline insulator Pb0.5Sn0.5Te

Kejing Ran, Ruidan Zhong, Tong Chen, Yuan Gan, Jinghui Wang, B. L. Winn, A. D. Christianson, Shichao Li, Zhen Ma, Song Bao, Zhengwei Cai, Guangyong Xu, J. M. Tranquada, Genda Gu, Jian Sun, and Jinsheng Wen
Phys. Rev. B 97, 220502(R) – Published 15 June 2018

Abstract

We present inelastic neutron scattering results of phonons in (Pb0.5Sn0.5)1xInxTe powders, with x=0 and 0.3. The x=0 sample is a topological crystalline insulator, and the x=0.3 sample is a superconductor with a bulk superconducting transition temperature Tc of 4.7 K. In both samples, we observe unexpected van Hove singularities in the phonon density of states at energies of 1–2.5 meV, suggestive of local modes. On cooling the superconducting sample through Tc, there is an enhancement of these features for energies below twice the superconducting-gap energy. We further note that the superconductivity in (Pb0.5Sn0.5)1xInxTe occurs in samples with normal-state resistivities of order 10 mΩcm, indicative of bad-metal behavior. Calculations based on density functional theory suggest that the superconductivity is easily explainable in terms of electron-phonon coupling; however, they completely miss the low-frequency modes and do not explain the large resistivity. While the bulk superconducting state of (Pb0.5Sn0.5)0.7In0.3Te appears to be driven by phonons, a proper understanding will require ideas beyond simple BCS theory.

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  • Received 12 April 2018

DOI:https://doi.org/10.1103/PhysRevB.97.220502

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Kejing Ran1, Ruidan Zhong2,3,*, Tong Chen1, Yuan Gan1, Jinghui Wang1, B. L. Winn4, A. D. Christianson4, Shichao Li1, Zhen Ma1, Song Bao1, Zhengwei Cai1, Guangyong Xu2,†, J. M. Tranquada2, Genda Gu2, Jian Sun1,5,‡, and Jinsheng Wen1,5,§

  • 1National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
  • 2Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory (BNL), Upton, New York 11973, USA
  • 3Materials Science and Engineering Department, Stony Brook University, Stony Brook, New York 11794, USA
  • 4Neutron Scattering Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee 37831, USA.
  • 5Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China

  • *Present address: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
  • Present address: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
  • jiansun@nju.edu.cn
  • §jwen@nju.edu.cn

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Issue

Vol. 97, Iss. 22 — 1 June 2018

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