Magnetic field-driven superconductor–insulator transition in boron-doped nanocrystalline chemical vapor deposition diamond

Abstract

The systematics of the suppression of superconductivity with increasing magnetic field in boron-doped nanocrystalline chemical vapor deposition diamond is studied in a broad temperature range. At the temperature of T S0 which is above the critical temperature, a plateau is observed in the resistivity versus temperature curve ͑T͒ taken at zero magnetic field. When a magnetic field of B = B SN ͑N =1,2, ... ,5͒ is applied, the plateau moves to low temperature with the thermoresistivity maximum located at T SN ͑N =1,2, ... ,5͒. The ͑B͒ curves, measured at different temperatures around T SN , intersect in the-B plane at the field of B = B SN. By tuning B SN from 0 to 5 T, a series of plateaus in the-T plane and the corresponding intersections in the-B plane are observed. The intersections quadratically chain up in the-B plane, separating the superconducting from the insulating region. The thermoresistivity maxima exponentially group up in the-T plane, thus defining a phase fluctuation zone. The phase boundary, composed of the intersections and separating the superconducting states from the insulating state, is shown to be a generic consequence of granularity.

Metal–Bosonic Insulator–Superconductor Transition in Boron-Doped Granular Diamond

“…The resistivity decreases as temperature goes down, and reaches, at around 40 K, a low residual value of $0:005-0:009 m, which corresponds to a conductivity about 10 3 times larger than the Mott minimum metallic conductivity $e 2 =@a (the distance between atoms in diamond a $ 1:5 # A). The residual resistivity is much lower than that of often reported resistivity values of microcrystalline and/or nanocrystalline diamond films [22][23][24][25] synthesized with microwave plasma-assisted chemical vapor deposition (MPCVD) method, suggesting good intergrain contacts. Our HDD thick layers were directly deposited on top of the insulating UDD ''substrates,'' and thus no seeding with undoped nanodiamonds was employed to promote the diamond nucleation as in MPCVD.…”

“…Localized bosonic islands, absorbing ''metallic'' fermions [ Fig. 1(b), panel (2)], are thus responsible for the metalbosonic insulator transition at T c (local) with embedded localized superconducting islands [24,25]. With decreasing temperatures bosonic islands continue to grow [ Fig.…”

“…0. In strongly disordered superconductors situated in the vicinity of IMT [24,25], the high degree of disorder may result in the formation of localized bosonic islands occurring at different T c (local), i.e., spatially different T c (local) [30]. Suppression of conductivity N !…”

“…Suppression of conductivity N ! 0 is, therefore, a gradual process, giving rise to a bump rather than a sharp peak superimposed within highly resistive background [24,25] In a two-resistor (normal and superconducting) model, N is connected in parallel to S . Electrical transport can be then approximated as [ Fig.…”

Superconductor-insulator transition driven by pressure-tuned intergrain coupling in nanodiamond films

“…2(a). Along with the change of the temperature coefficient of resistivity from negative to positive, ρ(T) demonstrates a maximum prior to the superconducting state (ρ = 0) [29]. Such a ρ(T) maximum has been generally observed in granular disordered superconductors.…”