Journal
PHYSICAL REVIEW B
Volume 97, Issue 22, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.97.220502
Keywords
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Funding
- MOST of China [2016YFA0300404, 2015CB921202]
- NSFC [11674157, 51372112, 11574133]
- NSF Jiangsu province [BK20150012]
- Fundamental Research Funds for the Central Universities [020414380105]
- Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase)
- Office of Basic Energy Sciences, U.S. Department of Energy [DE-SC0012704]
- Center for Emergent Superconductivity, an Energy Frontier Research Center, headquartered at BNL - U.S. Department of Energy [DE-2009-BNL-PM015]
- Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy
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We present inelastic neutron scattering results of phonons in (Pb0.5Sn0.5)(1-x) In-x Te 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 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)(1-x) In-x Te occurs in samples with normal-state resistivities of order 10 m Omega 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 (Pb0.5Sn0.5)(0.7)In0.3Te appears to be driven by phonons, a proper understanding will require ideas beyond simple BCS theory.
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