Anomalous Anisotropy in Superconducting Nanodiamond Films Induced by Crystallite Geometry

Phase Slips and Metastability in Granular Boron-doped Nanocrystalline Diamond Microbridges

“…1b of that paper shows a grain boundary spanning the entire vertical extent of the film. Other works [22,23] have also confirmed the columnar nature of the grains in similarly grown films. The general superconducting properties of BNCD (T c ∼ 4 K and ξ ∼ 10 nm) [12] are similar to bulk single crystalline samples [24] but the detailed behavior is modified by the granular microstructure [22,23], which is unusual for a superconducting material in that columnar grains extend vertically through the entire film.…”

“…Other works [22,23] have also confirmed the columnar nature of the grains in similarly grown films. The general superconducting properties of BNCD (T c ∼ 4 K and ξ ∼ 10 nm) [12] are similar to bulk single crystalline samples [24] but the detailed behavior is modified by the granular microstructure [22,23], which is unusual for a superconducting material in that columnar grains extend vertically through the entire film. Indeed, we have previously seen a 3D-0D-3D dimensional crossover in the fluctuation conductivity arising from the granularity [12,25].…”

Weak Electron Irradiation Suppresses the Anomalous Magnetization of N‐Doped Diamond Crystals

“…Several recent studies indicate a granular nature of the samples’ structure and of the SC phase. [ 12–15 ] The granular nature of the SC phase and localized disorder may play an important role as recently reported experimental facts indicate, namely: a) not always there is a clear correlation between the B‐concentration threshold for the metal–insulator transition and the one for SC, [ 16 ] and b) there is no simple dependence between the free‐carrier concentration and the critical temperature characterized by transport measurements. [ 17 ]…”

“…Several recent studies indicate a granular nature of the samples' structure and of the SC phase. [12][13][14][15] The granular nature of the SC phase and localized disorder may play an important role as recently reported experimental facts indicate, namely: a) not always there is a clear correlation between the B-concentration threshold for the metal-insulator transition and the one for SC, [16] and b) there is no simple dependence between the free-carrier concentration and the critical temperature characterized by transport measurements. [17] Another open issue in the SC puzzle of doped diamond is the fact that implanting boron into diamond via irradiation does not trigger SC at least above 2 K. [18] It has been argued that this irradiation process does not trigger SC because of the produced defects that remained in the diamond lattice after ion irradiation.…”

Effects of Rashba-spin–orbit coupling on superconducting boron-doped nanocrystalline diamond films: evidence of interfacial triplet superconductivity

“…Even more notable is the variation between scanning tunnelling microscopy (STM) measurements of this system; although initial STM studies have shown predominantly s-wave singlet pairing 22 , more recent investigations have demonstrated a range of unexpected findings such as anisotropic tunnelling spectra 23 , inhomogeneous gap structure across grains 24 , finite energy resonances within the vortex core 25 and most notably, evidence of a mixture of Bardeen-Cooper-Schrieffer (BCS) and non-BCS pairing 26 . Even more intriguing is the fact that superconducting boron doped diamond films have already demonstrated several of the crucial features of a triplet superconducting system including an unusually high and anisotropic upper critical field 27 and a temperature independent nuclear magnetic resonance (NMR) Knight shift 28,29,30 . Furthermore, signatures of a ferromagnetic grain boundary 21 have been claimed for this system however the under lying mechanism for triplet pair formation was not well established.…”