Nanowire Acting as a Superconducting Quantum Interference Device

We present the results from an experimental study of the magnetotransport 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 that underlie the operation of a superconducting quantum interference device.

Figure 1

$R$ vs $T$ obtained from wire 99Fe whose width is 100 nm, together with data from a similarly prepared $500\mu \mathrm{m}$ wide film. $T_c^{\mathrm{wire}}=2.8\mathrm{K}$ and $T_c^{\mathrm{film}}=2.7\mathrm{K}$. Inset: A scanning electron micrograph (SEM) of a typical device.

Figure 2

$R$ vs $B$ at $T=0.012\mathrm{K}$ for wire 99Nb. A smooth background, shown by the bold curve, is subtracted from the data to obtain the oscillatory part shown in Fig. 4a. Inset: $R$ vs $B$ displayed up to our highest accessible $B$ field of 12 T.

Figure 3

$R$ vs $B$ data from four states, displayed in a narrow $B$ range for clarity.

Figure 4

(a) $R_{\mathrm{osc}}$ vs $B$ taken at $T=0.012$ (top trace) and 1 K (shifted for clarity by $-4\mathrm{k}\Omega$), from wire 99Nb. (b) $T$ dependence of the amplitude of $R_{\mathrm{osc}}$ vs $B$ peaks at $B=0.13$ and $5.3\mathrm{T}$, normalized to their value at $T=0.012\mathrm{K}$. (c) FFT traces obtained from isotherms of $R_{\mathrm{osc}}$ vs $B$ in the interval 0–1.7 T, taken at $T=0.012$, 0.2, 0.4, 0.6, 0.8, and 1 K. The location of the dominant peak, $8.61/T$, corresponding to the main frequency of the oscillations, remains constant over the entire $T$ range, while its height decreases sharply with increasing $T$.