Structural and ferromagnetic properties in Mn implanted, p-type Si were investigated. High resolution structural analysis techniques like synchrotron X-ray diffraction revealed the formation of MnSi 1.7 nanoparticles already in the as implanted samples. Depending on the Mn-fluence, the size increases from 5 nm to 20 nm upon rapid thermal annealing. No significant evidence is found for Mn substituting Si sites either in the as-implanted or annealed samples. The observed ferromagnetism yields a saturation moment of 0.21 μ B per implanted Mn at 10 K, which could be assigned to MnSi 1.7 nanoparticles as revealed by a temperature dependent magnetization measurement.

In a variety of superconductors, mostly in two-dimensional (2D) and one-dimensional (1D) systems, the resistive superconducting transition RðTÞ demonstrates in many cases an anomalous narrow RðTÞ peak just preceding the onset of the superconducting state R ¼ 0 at T c . The amplitude of this RðTÞ peak in 1D and 2D systems ranges from a few up to several hundred percent. In three-dimensional (3D) systems, however, the RðTÞ peak close to T c is rarely observed, and it reaches only a few percent in amplitude. Here we report on the observation of a giant ($ 1600%) and very narrow ( $ 1 K) resistance peak preceding the onset of superconductivity in heavily boron-doped diamond. This anomalous RðTÞ peak in a 3D system is interpreted in the framework of an empirical model based on the metal-bosonic insulator-superconductor transitions induced by a granularity-correlated disorder in heavily doped diamond. DOI: 10.1103/PhysRevLett.110.077001 PACS numbers: 74.70.Wz, 71.30.+h, 74.25.Àq, 74.62.En Since the 1950s [1], a puzzling anomalous increase of resistance, RðTÞ, preceding the superconducting transition, has been reported in some superconducting systems situated not yet in the vicinity of the insulator-metal transition (IMT) with relatively low residual resistance. At first, the increase was only observed at the level of a few percent. Later on, in thin films [2][3][4] and 1D whiskers and wires [5,6], similar effects were also found, with a considerably higher amplitude of the RðTÞ anomaly: 16% and 160%. With the discovery of quasi-2D cuprates, the RðTÞ peak around T c was also reported for these lowdimensional materials, such as NdCeCuO [7], BiSrCaCuO [8,9], and LaSrCuO [10,11], with the peak amplitude reaching 400%-700%. In 2D and 1D microstructures [6,[12][13][14][15][16], made from conventional superconducting materials (mostly Al), a narrow resistance peak close to T c was also observed, with the peak amplitude reaching the 400% level.Different models were used to explain the nature of the anomalous RðTÞ peak: normal-metal-superconductor boundaries, disorder and fluctuations, vortex dynamics and Josephson coupling in layered systems, charge imbalance, and competition between superconducting and insulating states in 2D systems [1,2,4,6,8,[12][13][14]16,17].All these observations of the RðTÞ peak around T c and the corresponding models and theories, formulated to explain the corresponding experimental data, are very much linked to the reduced dimensionality of the investigated systems: 2D or/and 1D. We have found reports on the RðTÞ peak for 3D-like metallic Cu-Zr glasses only in a couple of previous publications [17,18] with a quite small RðTÞ peak amplitude-less than 3%. We present here our novel observations of the giant RðTÞ peak in 3D boron-doped granular diamond, which are very different from previously reported data in the following important aspects.First, the effect has a giant amplitude: the peak resistance value exceeds the residual resistance close to T c by 550%-1600%, which is a much higher value tha...

Strong granularity-correlated and intragrain modulations of the superconducting order parameter are demonstrated in heavily boron-doped diamond situated not yet in the vicinity of the metal-insulator transition. These modulations at the superconducting state (SC) and at the global normal state (NS) above the resistive superconducting transition, reveal that local Cooper pairing sets in prior to the global phase coherence.

Water electrolysis shows great promise for the low-cost mass production of high-purity hydrogen. The relatively high dissociation energy of water, however, often results in rather sluggish kinetics of the hydrogen evolution reaction (HER) in alkaline conditions, even for the case of state-of-the-art Pt-based electrocatalysts.Here, we show the high efficiency of the hybrids of PtRu nanoclusters (NCs) and black phosphorus (BP) nanosheets in HER. Our PtRu NCs/BP electrocatalysts demonstrate a HER activity of 88.5 mA cm -2 at -70 mV in 1 M KOH, which is higher than that of commercial Pt/C by one order of magnitude. The observed extraordinarily high HER activity of the PtRu NCs/BP hybrids is interpreted in the framework of density functional theory. Theoretical modeling indicates that the electronic interaction between BP and PtRu NCs speeds up the dissociation of water and optimize the adsorption strength for H* species, giving rise to the remarkably high HER activity of the PtRu NCs/BP hybrids.

Superconducting nanowires currently attract great interest due to their application in single-photon detectors and quantum-computing circuits. In this context, it is of fundamental importance to understand the detrimental fluctuations of the superconducting order parameter as the wire width shrinks. In this paper, we use controlled electromigration to narrow down aluminium nanoconstrictions. We demonstrate that a transition from thermally assisted phase slips to quantum phase slips takes place when the cross section becomes less than ∼150 nm2. In the regime dominated by quantum phase slips the nanowire loses its capacity to carry current without dissipation, even at the lowest possible temperature. We also show that the constrictions exhibit a negative magnetoresistance at low-magnetic fields, which can be attributed to the suppression of superconductivity in the contact leads. These findings reveal perspectives of the proposed fabrication method for exploring various fascinating superconducting phenomena in atomic-size contacts.

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