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> Nanotech forum > Nanotech > Anomalous superconducting wires
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Anomalous superconducting wires |
Alexey
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Mon Apr 2 04:58:18 2007
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Anomalous superconducting wires |
| Classification of partially measured and anomalous nanowires |
| Created: Fri May 4 07:36:11 2007
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Alexey
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Mon Apr 2 04:58:18 2007
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RE: Anomalous superconducting wires |
samples not included on the diagram:
070404j (DOE NOT CONTRADICT)
acts as a superconducting wire with reduced Tc; (d/dT)(d/dT)(lnR)<0 as for superconducting wires; not measured below 1.4K. Not in contradiction with our main conclusions;
013002b (DOE NOT CONTRADICT)
acts as a superconducting wire with reduced Tc; (d/dT)(d/dT)(lnR)<0 as for superconducting wires; not measured below 1.4K. Not in contradiction with our main conclusions;
070404l (DOE NOT CONTRADICT)
acts as a superconducting wire with reduced Tc; (d/dT)(d/dT)(lnR)<0 as for superconducting wires; not measured below 1.4K. Not in contradiction with our main conclusions;
101304d (DOE NOT CONTRADICT)
acts as a superconducting wire with reduced Tc; (d/dT)(d/dT)(lnR)<0 as for superconducting wires; not measured below 1.4K. Not in contradiction with our main conclusions;
013002d (DOE NOT CONTRADICT)
acts as a superconducting wire with reduced Tc; (d/dT)(d/dT)(lnR)<0 as for superconducting wires; not measured below 1.4K. Not in contradiction with our main conclusions; |
| Created: Fri May 4 07:38:06 2007
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Alexey
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RE: Anomalous superconducting wires |
Samples which might be considered anomalous:
101503d - The R(T) is funny, maybe it has a "tail"? The dV(I)/dI doesn't really show anything out of the ordinary. Unfortunately, this wire burned before we could make a complete characterization. Was measured only down to 1.5K. Might be a non-homogeneous sample with two transition, the second transition being measured only partially. THIS SAMPLE IS NOT IN CONTRADICTION TO CONCLUSIONS DERIVED FROM THE DIAGRAM, SINCE THE SAMPLE WAS NOT MEASURED DOWN TO LOW TEMPERATURES.
041204m - R(T) can seemingly be described by LAMH + QPS fit. But notice that the data actually goes above the fit and then below. So it's not exactly a straight-line "tail". Maybe we are seeing a couple different sections going superconducting at different temperatures. The dV(I)/dI curves certainly show some funny multiple peaks at high bias. This is clearly non-homogeneous sample. DOES NOT CONTRADICT OUR CONCLUSIONS. |
| Created: Fri May 4 07:40:51 2007
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Alexey
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RE: Anomalous superconducting wires |
070404g - just not enough data to determine state of wire. measured only down to 1.5K, then burned. NOT IN CONTRADICTION.
013002d - Initially measured down to 1.5K, showed features typical for superconducting samples (i.e. negative curvature on the ln(R) vs. T plot), but the resistance was still very high (of the order of Rn) at 1.5K. (Rn=4.5KOhm). Then the sample changed, oxidized perhaps. Then the sample was measured to 0.3K. The R(T) curve looks insulating (there is a zero-bias peak in resistance)but dV(I)/dI curves have a deep minimum, like a superconducting wire, with a very small zero-bias peak superimposed and two weakly defined critical current peaks. This wire probably became inhomogeneous dues to uneven oxidation or accidental high bias current passed through it. AS INHOMOGENEOUS SAMPLE, IT DOES NOT CONTRADICT THE DIAGRAM PAPER CONCLUSIONS.
101503f - For this samples the R(T) curves looks insulating but dV(I)/dI curves have a deep minimum, like a superconducting wire, with a very small zero-bias peak superimposed. Maybe is also slightly inhomogeneous. The evidence for inhomogeneity is not very pronounced, but there is a feature on dV/dI vs. I that looks like a second critical current . Rn=4.95kOhm. The sample acts insulating at low temp, low bias. MIGHT BE CONTRADICTING SAMPLE. Do we have more data on it, including pictures and also more curves. |
| Created: Sat May 5 20:23:17 2007
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Alexey
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RE: Anomalous superconducting wires |
| 121305g -- Looks anomalous and possibly contradicting. Rn=5.5kOhm. Resistance drops down to 3.8kOhm (at 0.3K), but with positive curvature on the dV/dI(I) curve. In other words the sample shows a QPS-like tail. Anomalous and contradicting sample. More data needed. What is the length of this wire? |
| Created: Sat May 5 22:41:01 2007
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Alexey
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RE: Anomalous superconducting wires |
082905f - sample appears superconducting, but was only measured down to 1.4K, then burned. Rn=5kOhm. NOT CONTRADICTING.
082905f - Rn=4.4 kOhm. Looks superconducting.
121801c - Rn=3.2kOhm. Appears superconducting. Measured only down to 1.4K. NOT CONTRADICTING.
081105b - Rn=2.8kOhm. Appear superconducting. Not measured below T=1.4K. NOT CONTRADICTING.
101304a - Rn=2.6kOhm. Similar to superconducting samples, but did not go to low resistance down to 0.3K. Show R=916 Ohms at T=0.3K. Sample shows a second step on R(T). Possibly non-homogeneous. Need to see dV/dI(I) to confirm non-homogeneity. NOT CONTRADICTING, SINCE Rn<h/4e^2 and the sample shows strong signature of superconducting behavior, including d^2(ln(R))/dT^2<0 (i.e.negative curvature).
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| Created: Sun May 6 00:02:58 2007
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Tony Bollinger
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Mon Apr 2 05:22:16 2007
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RE: Anomalous superconducting wires |
Translation of samples shown in "Inhomogenous Samples Graph.ogg"
A = 031027u1, Rn = 3.15 kOhms, L = 474 nm
B = 020904a, Rn = 3.18 kOhms, L = 414 nm
C = 040406a, R = 3.04 kOhms, L = ? (100 nm substrate was used)
D = 020904e, Rn = 7.29 kOhms, L = 399 nm
E = 020904b, Rn = 2.79 kOhms, L = 435 nm
F = 031027w2, Rn = 9.10 kOhms, L = 440 nm
G = 041204g, Rn = 7.89 kOhms, L = 455 nm
H = 121305g, Rn = 5.72 kOhms, L = ? (100 nm substrate was used)
Most are long wires samples, which is probably why their curves appear lumpy. 040606a and 121305g may be interesting. |
| Created: Mon May 7 19:41:01 2007
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Tony Bollinger
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Mon Apr 2 05:22:16 2007
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RE: Anomalous superconducting wires |
| I meant 040406a and 121305g may be interesting. |
| Created: Mon May 7 19:42:24 2007
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Alexey
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Mon Apr 2 04:58:18 2007
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!!Aging of wires: big questions!! |
yes, let us test the aging process like this:
measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day- measure R(T), keep it in air for one day-
Hope we will learn something from this aging investigation.
Some important questions are:
-Can a superconducting sample become insulating by aging?
-Can an insulating sample become granular and thus superconducting????????
(Remember, Tony demonstrated that granular samples can be superconducting even if there resistance is much bigger than 6.5 kOhm. So if a sample is insulating and Rn=9kOhm for example, we can let it oxidize (if oxidation goes fast enough, which is not know yet of course), and so the resistance will increase somewhat, say to Rn1=11kOhm. But this sample will be granular now, since oxidation is usually not homogeneous. Thus, due to Tony's result, this wire might act as a partically superconducting wire!!!) |
| Created: Fri Jun 22 01:30:45 2007
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