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A highly focused electron beam can be used to shape nanodevices. We demonstrate electron beam etching of nanoholes through multiwalled carbon nanotubes (MWNTs) and niobium nanowires. Nanoholes, as small as ∼2.5 nm in diameter, can be reproducibly fabricated. This technique can also be used to fabricate constrictions and larger nanoholes in MWNTs. We argue that with some improvement, this technique might be used to pattern suspended graphene by the removal of targeted single atoms. [ABSTRACT FROM AUTHOR]

Nanowires of niobium, platinum and indium–lead In 88 Pb 12 alloy with diameters of 4.2, 3.6 and 8 nm, respectively, were grown in quantized vortices of superfluid helium, and the dependences of their resistance on temperature have been studied. Through a detailed comparison of these dependences we present evidence that superconducting niobium wires allow a high rate of quantum phase slip. This phase slippage leads to a phase transition to an insulating state at T → 0. [ABSTRACT FROM AUTHOR]

Phase slips are topological fluctuations that carry the superconducting order-parameter field between distinct current-carrying states. Owing to these phase slips, superconducting nanowires acquire electrical resistance. In such wires, it is well known that at higher temperatures phase slips occur through the process of thermal barrier-crossing by the order-parameter field. At low temperatures, the general expectation is that phase slips should proceed through quantum tunnelling events, which are known as quantum phase slips. However, resistive measurements have produced evidence both for and against the occurrence of quantum phase slips. Here, we report evidence for the observation of individual quantum phase-slip events in homogeneous ultranarrow wires at high bias currents. We accomplish this through measurements of the distribution of switching currents for which the width exhibits a rather counter-intuitive, monotonic increase with decreasing temperature. Importantly, measurements show that in nanowires with larger critical currents, quantum fluctuations dominate thermal fluctuations up to higher temperatures. [ABSTRACT FROM AUTHOR]

A thin-film Fabry-Perot superconducting resonator is used to reveal the Little and Parks (LP) effect [Phys. Rev. Lett. 9, 9 (1962)], even at temperatures much lower than the critical temperature. A pair of parallel nanowires is incorporated into the resonator at the point of the supercurrent antinode. As the magnetic field is ramped, Meissner currents develop, changing the resonance frequency of the resonator. The LP oscillation is revealed as a periodic set of distorted parabolas observed in the transmission of the resonator and corresponds to the states of the wire loop having different vorticities. We also report a direct observation of single and double phase slip events. [ABSTRACT FROM AUTHOR]

The article reports on the study by Astafiev and colleagues which shows that quantum theory can explain the tunneling of magnetic flux across a nanowire in a superconducting system. It states that Astafiev and his colleagues developed a superconducting quantum bit (qubit) that was proposed by Maooj and Harmans. It says that the study paves the way for applications of nanowires supporting CQPS in quantum computing and metrology.

We present a study of superconducting nanowires shunted with an external resistor, geared towards understanding and controlling coherence and dissipation in nanowires. The dynamics is probed by measuring the evolution of the V-I characteristics and the distributions of switching and retrapping currents upon varying the shunt resistor and temperature. Theoretical analysis of the experiments indicates that as the value of the shunt resistance is decreased, the dynamics turns more coherent, presumably due to stabilization of phase-slip centers in the wire, and furthermore the switching current approaches the Bardeen's prediction for equilibrium depairing current. By a detailed comparison between theory and experiment, we make headway into identifying regimes in which the quasi-one-dimensional wire can effectively be described by a zero-dimensional circuit model analogous to the resistively and capacitively shunted Josephson junction model of Stewart and McCumber. Aside from its fundamental significance, our study has implications for a range of promising technological applications. [ABSTRACT FROM AUTHOR]

We report on observations of a superconductor-normal pulsing regime in microwave (GHz) coplanar waveguide resonators consisting of superconducting MoGe films interrupted by a gap that is bridged by one or more suspended superconducting nanowires. This regime, which involves MHz-frequency oscillations in the amplitude of the supercurrent in the resonator, is achieved when the steady-state amplitude of the current in the driven resonator exceeds the critical current of the nanowires. Thus we are able to determine the temperature dependence of the critical current, which agrees well with the corresponding Bardeen formula. The pulsing regime manifests itself as an apparent "crater" on top of the fundamental Lorentzian peak of the resonator. Once the pulsing regime is achieved at a fixed drive power, however, it remains stable for a range of drive frequencies corresponding to subcritical steady-state currents in the resonator. We develop a phenomenological model of resonator-nanowire systems from which we are able to obtain a quantitative description of the amplitude oscillations and also, inter alia, to investigate thermal relaxation processes in superconducting nanowires. For the case of resonators comprising two parallel nanowires and subject to an external magnetic field, we find field-driven oscillations of the onset power for the amplitude oscillations, as well as the occurrence (for values of the magnetic field that strongly frustrate the nanowires) of a distinct steady state in which the pulsing is replaced by stochastic amplitude fluctuations. We conclude by giving a brief discussion of how circuit-quantum electrodynamics-based systems have the potential to facilitate nondestructive measurements of the current-phase relationship of superconducting nanowires and, hence, of the rate at which quantum phase slips take place in superconducting nanowires. [ABSTRACT FROM AUTHOR]

Quantum phase slippage (QPS) in a superconducting nanowire is a new candidate for developing a quantum bit [Mooij et al. New J. Phys.2005, 7, 219; Mooij et al. Nat. Phys.2006, 2, 169; Khlebnikov http://arxiv.org/abs/quant-ph/0210019 2007]. It has also been theoretically predicted that the occurrence of QPS significantly changes the current-phase relationship (CPR) of the wire due to the tunneling between topologically different metastable states [Khlebnikov Phys. Rev. B2008, 78, 014512]. We present studies on the microwave response of the superconducting nanowires to reveal their CPRs. First, we demonstrate a simple nanowire fabrication technique, based on commercially available adhesive tapes, which allows making thin superconducting wire from different metals. We compare the resistance vs temperature curves of Mo76Ge24and Al nanowires to the classical and quantum models of phase slips. In order to describe the experimentally observed microwave responses of these nanowires, we use the McCumber−Stewart model [McCumber J. Appl. Phys.1968, 39, 3113; Stewart Appl. Phys. Lett.1968, 12, 277], which is generalized to include either classical or quantum CPR. [ABSTRACT FROM AUTHOR]