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Séminaire QUEST

Jeudi 08 février à 9h30,
Salle Rémy Lemaire, K223

Orateur : Gufei ZHANG (KU Leuven, Belgium)
"Black Diamond : A Piece of Jewelry for Superconductivity"

Abstract

Since the preparation of synthetic diamond by Dr. H. T. Hall at General Electric in 1954, industry has benefited more and more from this material. With a low fabrication cost, synthetic diamond brings in nearly all the unique advantages of natural diamond, e.g., the robust mechanical strength, the extraordinarily high thermal conductivity, the remarkable resistance to contamination and chemical etching, and so on. Besides, the remarkable electronic properties of blue diamond (lightly boron-doped diamond), has made this cost-effective semiconductor a promising candidate for the 21st-century microelectronics and power electronics. After 2004, the application range of artificial diamond has been further extended owing to the superconductivity discovered in black diamond (heavily boron-doped diamond).[1,2]
Black diamond also provides a powerful stage for solving some interesting puzzles, which are not only relevant for practical concerns but also significant in fundamental science. The observation of superconductivity in bad conductors (doped insulators such as high temperature superconductors and black diamond) is an intriguing question directly linked to the origin of superconductivity.[3] In addition, the influence of disorder on the quantum condensate of Cooper pairs still remains an attractive topic, after accompanied the ever growing list of superconductors for nine decades. Note that as a result of the preparation method, synthetic black diamond is generally granular disordered. Here I will provide an overview of the superconductivity in black diamond. The granular nature of the superconductivity in diamond will be demonstrated by showing the electrical transport, magnetic, specific heat and local superconducting properties of this material.[4-6] Our observations of various bosonic anomalies in diamond are interpreted as a result of quantum confinement and coherence effects in the presence of intrinsic and extrinsic granularity.[7-9] Our data, obtained for black diamond, provide a reference for understanding the superconductivity in other granular disordered systems. In the case of time allowance, the audience will be briefed on our recent observations of electronically entangled superconducting and ferromagnetic orderings in hydrogenated black nanodiamond.[10]

[1] E. A. Ekimov, et al. Nature 428, 542 (2004).
[2] Y. Takano, et al. Appl. Phys. Lett. 85, 2851 (2004).
[3] E. Bustarret, Phys. Status Solidi A 205, 997 (2008).
[4] G. Zhang, et al. J. Appl. Phys. 108, 013904 (2010).
[5] G. Zhang, et al. Phys. Rev. B 84, 214517 (2011).
[6] G. Zhang, et al. Adv. Mater. 26, 2034 (2014).
[7] G. Zhang, et al. Phys. Rev. Lett. 110, 077001 (2013).
[8] G. Zhang, et al. Phys. Rev. Appl. 6, 064011 (2016).
[9] G. Zhang, et al. ACS Nano 11, 11746 (2017).
[10] G. Zhang, et al. ACS Nano 11, 5358 (2017).

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