کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
702343 1460804 2012 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Hubbard-U and disproportionation in superconducting boron doped diamond
موضوعات مرتبط
مهندسی و علوم پایه سایر رشته های مهندسی مهندسی برق و الکترونیک
پیش نمایش صفحه اول مقاله
Hubbard-U and disproportionation in superconducting boron doped diamond
چکیده انگلیسی

Synthetic and natural diamonds containing small amounts of boron are conducting with apparent activation energy of 0.37 eV at high temperature and ≈ 0.01 eV at low temperature. If the boron/carbon ratio is increased above about 1‰, the higher activation energy starts to decrease to zero. By applying high pressure and high temperature Ekimov et al. managed to raise the B/C ratio above 1%. This material is superconducting below a few Kelvin. It is shown here that at low B/C ratio the MIR absorption at 0.37 eV can be identified with vertical Hubbard-U. Increasing the boron concentration Hubbard-U decreases to zero. Apparently B+/B− becomes more stable than B/B as a sub-lattice phase. It is shown that this is due to the smaller distance between the boron sites. The presence of B+, B, and B− in highly boron doped diamond is supported by NMR, Raman, and IR data in combination with simple calculations.

Figure optionsDownload as PowerPoint slideHighlights
► Activation energy (= 0.37 eV) in blue diamonds is identified as “Hubbard-U” for 2B → B+ + B−.
► B+ and B− sites are identified in the experimental data and in calculations.
► There are large sp2 components in the wavefunction of B+ and neutral B centers.
► At high concentration of B, U → 0 since the B+/B− subphase is stabilized relative to B/B.
► Superconductivity is due to the interaction between (B+/B−) and (B/B) electronic states, and phonons.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Diamond and Related Materials - Volume 26, June 2012, Pages 71–77
نویسندگان
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