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Structure-property correlations in a phase-pure high-temperature superconductor with a record BCS Tc = 55 K

Abstract

Here, we report the detailed structure-property correlations in the phase-pure robust B-doped Q-carbon high-temperature superconductor having a record Bardeen-Cooper-Schrieffer (BCS) superconducting transition temperature (Tc) of 55 K. This superconducting phase is a result of nanosecond laser melting and subsequent quenching of a highly super undercooled state of molten B-doped C. The temperature-dependent resistivity at different magnetic fields and magnetic susceptibility measurements indicate a type-II BCS superconductivity in B-doped Q-carbon thin films. The magnetic measurements indicate that the upper and lower critical fields follow Hc2(0)[1-(T/Tc)1.77] and Hc1(0) [1-(T/Tc)1.19] temperature dependence, respectively. The structure-property characterizations of B-doped Q-carbon indicate a high density of electronic states near the Fermi-level and large electron-phonon coupling. These factors are responsible for s-wave bulk type superconductivity with enhanced Tc in B-doped Q-carbon. The time-dependent magnetic moment measurements indicate that B-doped Q-carbon thin films follow the Anderson-Kim logarithmic decay model having high values of pinning potential at low temperatures. The crossover from two-dimensional to three-dimensional nature of Cooper pair transport at T/Tc = 1.02 also indicates a high value of electron-phonon coupling which is also calculated using the McMillan formula. The superconducting region in B-doped Q-carbon is enclosed by Tc = 55.0 K, Jc = 7.10\times108 A/cm2, and Hc2 = 9.75 T superconducting parameters. The high values of critical current density and pinning potential also indicate that B-doped Q-carbon can be used for persistent mode of operation in MRI and NMR applications. The Cooper pairs which are responsible for the high-temperature superconductivity are formed when B exists in the sp3 sites of C. The electron energy loss spectroscopy and Raman spectroscopy indicate a 75% sp3 bonded C and 70% sp3 bonded B in the superconducting phase of B-doped Q-carbon which has 27 at% B and rest C. The dimensional fluctuation and magnetic relaxation measurements in B-doped Q-carbon indicate its practical applications in frictionless motors and high-speed electronics. This discovery of high-temperature superconductivity in strongly bonded and lightweight materials by using non-equilibrium synthesis will provide the pathway to achieve room-temperature superconductivity.

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Publication details

The article was received on 18 Jan 2019, accepted on 16 Apr 2019 and first published on 16 Apr 2019


Article type: Paper
DOI: 10.1039/C9NR00562E
Citation: Nanoscale, 2019, Accepted Manuscript

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    Structure-property correlations in a phase-pure high-temperature superconductor with a record BCS Tc = 55 K

    A. Bhaumik and J. Narayan, Nanoscale, 2019, Accepted Manuscript , DOI: 10.1039/C9NR00562E

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