For instance there are reports on Ag added effects in YBCO , but superconducting YBCO already shows a decrease in resistivity before Tc.
What about a superconductor which shows a semiconducting like rise in resistivity before Tc? Will adding Ag necessarily make it metallic?
Addition of Ag may induce metalicity but that has nothing to do superconductivity. You know Ag although a good conductor does not become superconducting. In fact the metals that are not a very good conductor at higher temperature (viz. Nb, Sn, Pb etc.) becomes super conducting below Tc. To make a metallic sample superconducting you should try to have strong electron phonon coupling which can generate Cooper pairs necessary for superconductivity. This is valid only for conventional BCS superconductivity. For unconventional superconductivity we do not really know how to get a good superconductor but we know in order to have a high-T_c value one should perhaps start from an antiferromagnetic Mott insulator like cuprates. But this wisdom fails with Fe- based superconductors and also with heavy fermion superconductivity.
Thank you Sir, will it change the trend before Tc ??, ie suppose the compound has a semiconductor like rise before Tc , by adding Ag will this trend change to metallic while still preserving Superconductivity??
Do you mean that the resistivity of your sample goes up (like a semiconducor) first while cooling and then drops to zero or becomes superconductor? Why must you suppress the upward resistivity trend? It gets superconducting anyway. You never know before doing the experiment whether the addition of some element has the desired or the undesired property. Addition of Ag may suppress the upward trend but can also kill superconductivity. We cannot predict much in superconductivity not even in conventional superconductivity.
Actually Sir , in my case adding Ag does not affect neither the semiconducting rise nor the Tc , its just that the over all resistivity of the sample has decreased , but when i presented this result in a conference, one person has pointed out that adding Ag should change the semiconducting rise into metallic, i was thinking was that necessary.
What is your sample and what is its Tc value? I do not think that get an predictable behavior unless you know the details of what you are doing. If you dope Cu by Ag in cuprate superconductors then you know (only from experiments) that Tc goes down. But whether it also modifies normal state resistivity behavior you must do the experiment. I do not think that there is any viable theoy for that.
Sir, the sample is Nd1.85Ce0.15CuO4 and Ag is added 5% of weight, Tc still remains at 24K.
Yes Sir , that is in process.
The above mentioned results are in polycrystalline sample.
If you succeed in growing single crystals then please do contact me. We can do neutron scattering work together.
We are trying via Travelling solvent float zone method as well as flux growth
The addition of metallic nano-entities, especially the silver, will enhance the connectivity between grains and thus lead to enhance the superconducting properties in particular the critical current density.
An small amount of addition can lead to enhance a little bit the Tc and to reduce the resistivity in the normal state.
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