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Title: Unusual phonon density of states and response to superconducting transition in In-doped topological crystalline insulator Pb 0.5Sn 0.5Te

Here, we present inelastic neutron scattering results of phonons in (Pb 0.5Sn 0.5) 1–xIn xTe 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 T c 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 T c, there is an enhancement of these features for energies below twice the superconducting-gap energy. We further note that the superconductivity in (Pb 0.5Sn 0.5) 1–xIn xTe occurs in samples with normal-state resistivities of order 10 mΩ cm, 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 (Pb 0.5Sn 0.5) 0.7In 0.3Te appears to be driven by phonons, a proper understanding will require ideas beyond simple BCS theor
 [1] ; ORCiD logo [2] ;  [3] ;  [1] ;  [1] ;  [1] ;  [4] ;  [4] ;  [1] ;  [1] ;  [1] ;  [1] ;  [5] ;  [2] ;  [1] ;  [1]
  1. Nanjing Univ., Nanjing (China)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., Stony Brook, NY (United States); Princeton Univ., Princeton, NJ (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. Brookhaven National Lab. (BNL), Upton, NY (United States); National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 2469--9950
Grant/Contract Number:
SC0012704; 2009-BNL-PM015
Accepted Manuscript
Journal Name:
Phys. Rev. B
Additional Journal Information:
Journal Volume: 97; Journal Issue: 22; Journal ID: ISSN 2469--9950
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1454370