Nonlocal vortex motion in mesoscopic amorphous ${\mathrm{Nb}}_{0.7}{\mathrm{Ge}}_{0.3}$ structures

We study nonlocal vortex transport in mesoscopic amorphous ${\mathrm{Nb}}_{0.7}{\mathrm{Ge}}_{0.3}$ samples. A dc current $I$ is passed through a wire connected via a perpendicular channel, of a length $L=2–5\mu m$, with a pair of voltage probes where a nonlocal response $V_{\mathit{nl}}\propto I$ is measured. The maximum of $R_{\mathit{nl}}=V_{\mathit{nl}}∕I$ for a given temperature occurs at an $L$-independent magnetic field and is proportional to $1∕L$. The results are interpreted in terms of the dissipative vortex motion along the channel driven by a remote current and can be understood in terms of a simple model.

Figure 1

Local (lines, left-hand scale) and nonlocal (symbols, right-hand scale) response for the $L=2\mu \mathrm{m}$ channel at $T=1.4\mathrm{K}$ $(B_{c2}=2.95\mathrm{T})$ and $I=I_{01}=300,600,800\mathrm{nA}$. Inset: a photograph of the sample, with the designation of the leads and the definition of the coordinate system.

Figure 2

$R_{\mathit{nl}}\left(B\right)$ (left-hand scale) for an $L=3\mu \mathrm{m}$ channel at $T=0.8,1.6,2.6\mathrm{K}$ and $I=600\mathrm{nA}$, with the voltage resolution shown by the right-hand scale. The curves are offset for clarity. The meaning of $B_d$, $B_p$, and $R_p$ is indicated by the arrows.

Figure 3

Characteristic parameters of $R_{\mathit{nl}}$ for the three channel lengths. (a) $B_p\left(T\right)$ together with $B_{c2}\left(T\right)$, $B_{dl}\left(T\right)$, and $B_d\left(T\right)$ for the $L=2\mu \mathrm{m}$ channel. The dashed lines are guides for the eye. (b) $L{R}_p$ vs $T$. The solid lines represent the results of the calculations (using ${\eta }_{BS}$ and ${\eta }_T$, as indicated) explained in the text.