Journal
ACTA MATERIALIA
Volume 174, Issue -, Pages 153-159Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2019.05.013
Keywords
Q-carbon; BCS superconductivity; Shallow energy levels; Monochromated electron energy-loss spectroscopy; Carbon
Funding
- National Academy of Sciences, USA
- ARO [W911NF-16-2-0038]
- National Science Foundation [DMR-1735695, ECCS-1542015]
- State of North Carolina
- U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Technology Division
- U.S. Department of Energy [DE-AC05-00OR22725]
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We report the spectroscopic demonstration of the shallow-level energy states in the recently discovered B-doped Q-carbon Bardeen-Cooper-Schrieffer (BCS) high-temperature superconductor. The Q-carbon is synthesized by ultrafast melting and quenching, allowing for high B-doping concentrations which increase the superconducting transition temperature (T-c) to 36 K (compared to 4 K for B-doped diamond). The increase in T-c is attributed to the increased density of energy states near the Fermi level in B-doped Q-carbon, which give rise to superconducting states via strong electron-phonon coupling below T-c. These shallow-level energy states, however, are challenging to map due to limited spatial and energy resolution. Here, we use ultrahigh energy resolution monochromated electron energy-loss spectroscopy (EELS), to detect and visualize the newly formed shallow-level energy states (vibrational modes) near the Fermi level (ranging 30-100 meV) of the B-doped Q-carbon. With this study, we establish the significance of high-resolution EELS in understanding the superconducting behavior of BCS superconducting C-based materials, which demonstrate a phenomenal enhancement in the presence of shallow-level energy states. (C) 2019 Published by Elsevier Ltd on behalf of Acta Materialia Inc.
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