Nanowire Acting as a Superconducting Quantum Interference Device

Abstract

We present the results from an experimental study of the magneto-transport of superconducting wires of amorphous Indium-Oxide, having widths in the range 40 -120 nm. We find that, below the superconducting transition temperature, the wires exhibit clear, reproducible, oscillations in their resistance as a function of magnetic field. The oscillations are reminiscent of those which underlie the operation of a superconducting quantum interference device.PACS numbers: 74.78. Na, 85.35.Ds, 73.21.Hb The central challenge in the study of thin superconducting wires is to understand how superconductivity is affected when approaching the one-dimensional (1D) limit. Earlier studies have predicted that intrinsic thermal [1, 2] and quantum [3,4,5] fluctuations play an increasingly important role in this limit, causing the wires to remain resistive much below the superconducting transition temperature, T c . Recent theories [6,7], incorporating the effect of electron-electron interactions, describe the suppression of T c when approaching the 1D limit, which was observed in experiments [8].In recent years new experimental techniques enabling the fabrication of superconducting wires with a diameter approaching the 1D limit were developed. The experiments that followed [9] focused primarily on whether the quantum resistance for a Cooper-pair, R Q = h/4e 2 ≈ 6.45 kΩ (h is Planck's constant and e is the charge of the electron) is the resistance scale that solely controls the existence of superconductivity. While some works [9,10] provided evidence that wires with a normal state resistance R N < R Q are superconducting and those with R N > R Q become insulating at low T , this point is still under debate [11].In this letter we report on an experimental study of the magnetic field (B) dependence of the resistance of superconducting wires whose dimensions are close to the 1D limit. We find that, while a strong B drives our wires into an insulating state, the magnetoresistance is dominated by reproducible periodic oscillations similar to those observed in superconducting quantum interference devices (SQUIDs) [12]. We also find that wires with R N >> R Q can exhibit superconductivity.In order to fabricate our 1D wires we utilized the method of Bezryadin et al. [9], in which a non-conducting nanotube, suspended across a narrow gap etched in a semiconductor substrate, is used as a template on which the superconductor is deposited. There are two experimental differences between our work and that of Ref.[9]. First, instead of carbon, our nanotubes were made of WS 2 [13]. Being a semiconductor with a bandgap of about 2 eV [14], WS 2 nanotubes are electrically insulating at low T and do not create a parallel conduction channel. We have verified that the nanotubes are insulating before depositing the superconducting material.Second, and more importantly, for the disordered superconductor we chose amorphous indium-oxide (a:InO). This choice was influenced by several of its properties. Since a:InO is known to form relatively uniform, superco...

Nonlinear current-voltage characteristics due to quantum tunneling of phase slips in superconducting Nb nanowire networks

“…3(b), were indeed obtained using Eq. (4). The values extracted for the parameter R qp depend on the magnetic field and are all lower than R N going from ∼ 600 Ω at µ 0 H = 0.01 T to ∼ 800 Ω at µ 0 H = 0.14 T. This result is consistent with the fact that, since R qp represents the low-temperature residual resistance, [7] it should tend to R N when the applied magnetic field becomes larger.…”

“…[1][2][3][4][5][6][7][8] This great interest rose since superconducting nanowires involve fundamental phenomena such as macroscopic quantum tunneling and quantum phase transitions [9][10][11][12] and, in addition, they can find applications in classical [13] and possibly quantum information-processing devices [14,15] or they can be used as interconnects in electronic nanostructured devices. [16] The main point in the study of superconducting nanowires is to understand how their superconducting properties change when the 1D limit is approached.…”

“…[1,10] However, in the high-current (low-temperature) limit it simply reduces to [1,7,10] V QPS ∼ I 2µ−1 (4) with µ = R Q /R qp . Here R qp is a resistance of the order of R N [7] which can be considered as a fitting parameter.…”

Atom by atom: HRTEM insights into inorganic nanotubes and fullerene-like structures

“…Moreover, the difference in chirality inside the tubes, i.e., the existence of a tube containing adjacent chiral and nonchiral shells, could explain the mediocre electrical performance of the nanotubes, which were found to be much less conductive than the bulk material (39). This can in turn be attributed to the mobility of electrons within the different shells in the tube.…”

NbSi nanowire quantum phase-slip circuits: dc supercurrent blockade, microwave measurements, and thermal analysis

“…2,13 Ultranarrow nanowires have been developed in both these materials with effective diameters in the range 20-40 nm. [14][15][16] QPS in InO x has been demonstrated via spectroscopic measurements of E S in a QPS qubit, 2 while alternative evidence for QPS (in fact, for the dual effect of coherent tunneling of single Cooper pairs) has been observed in NbSi nanowires via quantum interference in a device dual to the SQUID consisting of two QPSJs joined by a superconducting island. 15 Preliminary signs of QPS 17,18 and of dual Shapiro steps 19 have been observed in a Ti nanowire, but only traces of steps are observed.…”