What is Superconductors: Definition and 146 Discussions

Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.
In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 90 K (−183 °C). Such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. The cheaply available coolant liquid nitrogen boils at 77 K, and thus the existence of superconductivity at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures.

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  1. H

    Knotted Solitions in multiband superconductors

    According to Prof Egor Babaev and others, it seems possible to have knotted solitons in certain superconductors. He has had numerous articles published in Physical Review and Nature. The most understandable one I've found is Hidden symmetry and knot solitons in a charged two-condensate Bose...
  2. C

    Superconductors and the Meissner Effect

    So I'm a little confused about the Meissner Effect. If we have both a perfect conductor and a superconductor (both above Tc) and place them in a magnetic field and lower their temperatures so they exhibit their respective properties, the magnetic field inside the perfect conductor persists...
  3. ViperSRT3g

    Experimenting with Superconductors and Pressures

    I apologize beforehand for my lack of experience in searching through scientific articles or journals. But I was reading an article about super conductors, and then the question popped into my head. Has anyone heard of an experiment that tested various known superconductors under different...
  4. 2

    How can type-I superconductors have a critical field value?

    Hello. I am reading about Flux pinning and I have read that only type-II superconductors can be used for that because there is no magnetic field in type-I superconductors (or rather they cannot be penetrated). If so, how can type-I superconducotrs still have a critical magnetic field strength...
  5. W

    Using what Liquid gas to cool TYPE I Superconductors?

    So, Liquid Nitrogen or Liquid Helium to cool Type I(Lead/Aluminum) superconductor? I know its best to use Liquid Helium, but can I use Liquid Nitrogen and go below the BC of those materials?
  6. G

    Progress in High Tc Superconductors: A Brief Overview

    Just curious if anyone knew about any progress with higher critical temperature superconductors, whether they're cuprates or metals, what is the mixture of elements, you know just any news. I was thinking about looking into making a high tc superconductor of my own and yes I know that if its...
  7. B

    How do superconductors convert frequency to voltage?

    I am doing some reading about superconductors and Josephson Junctions and was wondering about one of their exhibited behaviors. I read a statement claiming that if a frequency (AC current) is applied to the terminals of a Josephson Junction by microwave irradiation then the current of cooper...
  8. Demystifier

    Why does superconductors don't radiate?

    In ordinary conductors, electrons can lose energy by two mechanisms. First, by electron scattering on atoms of the lattice bulk, thus transferring energy to the bulk and increasing the bulk's temperature. This is the main contribution to the conductor resistance. But there is also the...
  9. P

    I Why superconductors have zero resistance

    Hi I know that BCS theory predicts Cooper pairs which move as a Bose condensate in superconductors. But why would scattering lead to a zero resisitance state because surely the Cpairs would provide resistance. I realize that superconductors have zero resistance but just can't really seee why?
  10. T

    Superconductors and induction - what are the posibilities?

    Hi all, I have a question which relates to induction and one potentially useful property of superconductors which seems to suggest one intriguing posibility. I won't say what just yet since my science is potentially a bit rusty, so don't want to sound like a fool. As I understand it, after...
  11. C

    High temperature superconductors

    What is the highest temperature a superconductor can work today?
  12. J

    Current in superconductors when a voltage is applied.

    Suppose you a have superconducting loop connected to a 9V battery. What is the current through it? With a resistance of 0Ω, V = IR gives ∞. I don't think that can be right... If it were, V=\frac{I}{nAe} would give an infinite velocity... Does that equation even apply to superconductors?
  13. A

    Superconductors - some general questions.

    I will be trying to build an electric motor using superconductors and I have some general concept questions in regards to how the behavior might be different from ordinary wires. 1. The Meissner effect, expulsion of magnetic fields from the superconductor. If you construct a solenoid out of...
  14. H

    What are Cooper pairs from superconductors

    I asked about superconductors in another paost, and what I got was how superconductivity is achieved, and how electrons are attracted together via interactions with atomic nuclei. My question is, what exactly is a cooper pair? To me, when I think of the word pair, I immediately imagine the...
  15. H

    How do electricity and superconductors work?

    Electricity has been a mysterious entity plaguing my mind since last year when I learned about it in class. I am unable to understand why electrons move the way they do when a circuit is formed, nor what is the driving force to make them do so (which is voltage difference, and I don't understand...
  16. C

    What is The real cause of meissner effect in superconductors?

    As i have learnt, the lenz's law is not the cause of the meissner effect.This can also be proved by some experiments.I was wondering what may be the real cause for the meissner effect? As i don't know the cause, i have no idea, in which part of physics i must post this query.
  17. D

    Article: Higgs Boson in Superconductors

    I ran into the following article by Varma, Higgs Boson in Superconductors http://arxiv.org/abs/cond-mat/0109409 Varma compares the Gross-Pitaevskii equation with the Higgs Lagrangian and calculates the elementary excitations. He shows that although symmetry is broken in both cases, Higgs...
  18. G

    Electron wavelength in superconductors

    What is a rough figure for the wavelength of the moving electrons in a superconductor? Or is there no easy answer for that?
  19. R

    Mechanism of high-temp. superconductors

    My prof. asked: "What is the mechanism that causes certain materials to exhibit superconductivity at temperatures much higher than around 25 kelvin?" then until now it remain a question to me?.. so anyone have an idea? thank you.
  20. F

    Superconductors and best conductors

    Hello Forum gold, silver, copper are the best electrical conductors are room temperature. But they cannot be superconductors: there is no finite, low critical temperature at which they become superconductors... But what if we could bring their temperature to 0 kelvin? I believe that all...
  21. R

    Current density inside superconductors

    Homework Statement consider an infinite superconducting slab of thickness 2d (-d<=z<=d), outside of which there is a given constant magnetic field parallel to the suface. Hx =Hz=0 hy= H0 (some value for z<d and z>-d) , with E vector= D vector=0 everywhere. compute H vector < J vector inside...
  22. P

    What is kinetic capacitance in superconductors or in solid state in general?

    What is "kinetic capacitance" in superconductors or in solid state in general? Hi, I would appreciate it if anyone could explain to me what "kinetic capacitance" is, particularly in the context of superconductors or solids. I understand "kinetic inductance" which comes from the kinetic...
  23. J

    Invention Idea - Cheap Room-Temperature Superconductors Now?

    "Invention" Idea - Cheap Room-Temperature Superconductors Now? I propose that if you encase a superconducting material along with liquid helium (or some other coolant) inside a Dewar flask or Thermos and then insert liquid helium, and then cool the superconductor+liquid helium once down to...
  24. J

    Help with Very High Temperature superconductors (28°C )

    Help with Very High Temperature superconductors (28°C!) Since several months researchers on www.superconductors.org have published results about Very High Temperature SuperConductors (VHTSC). A new result has been recently published: http://www.superconductors.org/28c_rtsc.htm I don't...
  25. T

    Learning about superconductors

    Well, right now I am a high school student taking AP Physics C, BC cac and AP chem and I want to self learn about superconductors. I have looked online and at my school library and have had little to no luck finding any documents that I can learn from. My goal is to learn about superconductors...
  26. M

    Type 1 Superconductors & Static B field density

    [credit to wikipedia] So it would appear that the type 1 meissner effect allows for the localized increase of magnetic flux density (as the displaced field must go somewhere, the B field is somewhat larger at the surfaces of the superconductor then elsewhere, and in fact is a higher value...
  27. N

    Are superconductors dia magnetic materials?

    are superconductors dia magnetic materials?? if so, what are similarities between them??
  28. D

    Flux Pinning/Heat Generation in Type II Superconductors

    I don't understand the mechanism by which "flux tubes" create heat, and are pinned by impurities in a type II superconductor. When Bc1<B<Bc2 I understand magnetic flux will penetrate the material in the form of flux tubes. Then the current in the superconductor exerts a force on these tubes...
  29. D

    Superconductors, ElectroMagnets and MagLevs

    Guys I have a problem. Maybe, it's is a stupid one, but I really need help to comprehend something. I'm writing a report about applications of superconductivity. I chose the MagLev trains applications. Let's say, everything was fine until I read about the Meissner Effect. Now I have my mind...
  30. khurram usman

    My knowledge of superconductors is limited to the fact that they are

    my knowledge of superconductors is limited to the fact that they are substances whose resistnce bcme zero below a certain temperature and current once established continues to flow indefinitely. a) how can substances behave as supercondictors?(i don't know the name of any...superconducting...
  31. A

    Why is it called fluctuation conductivity in superconductors?

    Why is it called "fluctuation conductivity" in superconductors? Hello, In the work of Aslamazov-Larkin and many more, conductivity of a superconductor is calculated from the time dependent Ginzburg-Landau (TDGL) theory. They call it "fluctuation conductivity" bellow and above critical...
  32. L

    Why some metals are not superconductors?

    Hello, I'm studying about superconductivity. So far I understand that the material needs have zero resistance and meissner effect to be a superconductor. But why materials such as copper or gold are not superconductors? I think it's something to do with some quantum effect like cooper...
  33. L

    By definition, superconductors are conductors with zero resistance at

    By definition, superconductors are conductors with zero resistance at low temperatures. Do superconductors exist ideally, i mean whether zero resistance is practically possible?
  34. P

    Irreversibility temperature in superconductors

    Hello, I would be grateful is someone could explain what the irreversibly temperature in type II superconductors is. I have just done some NMR experiments on MgB2 and get a lineshape change at the the irreversibility temperature as opposed to the field corrected Tc, so I believe it has...
  35. P

    Nonlocal electrodynamics of superconductors

    Hello, Conductivity \sigma (\omega, k) in Fourier space is defined by J(\omega, k)= \sigma (\omega, k) A(\omega, k) In most cases the local limit of k\rightarrow 0 is a good approximation particulalry in type I superconductors and HTC superconductors. I am interested in cases...
  36. I

    Where Can I Find Resources for Research in Superconductors and Nano-Tech?

    I am a freshman at Wright State University in Ohio. I am trying to decide where to eventually place my focus at. I understand it is early but I am one of those people who puts in 20 hours of "fun" study time on the side while still doing my college work. To me Superconductors, Genetic...
  37. O

    Why don't superconductors emit a lot of heat?

    Hi everyone, just a quick question. I just heard someone say a superconducting electromagnet does not produce heat, which I find very strange, since it seems that, since rate of heat energy being dissipated = voltage^2/resistance. Taking the limit as resistance goes to 0, with voltage held...
  38. C

    How Do Defects in Superconductors Affect Electron Flow?

    I have a question I'm unsure about. It's asking me to contrast the way defects in normal conductors impede the flow of electons whereas they facilitate the current in superconductors. I can explain why defects cause resistance in conductors and also why electrons encounter no resistance by...
  39. A

    What are the different types of superconductors and how do they work?

    As I understand it there are two types of superconductors, conventional and non-conventional. Conventional superconductors are explained by the BCS theory, my understanding of which being electrons pair up because the bending fields from their movement hold them together and there is not enough...
  40. K

    Reaching Absolute Zero: Methods to Achieve Superconductors

    I hear how people create superconductors by taking a metal and freezing it to Absolute Zero(0 Kelvin). What are some methods to get this sort of tempuature? Can anyone help?
  41. R

    Zero Resistivity in superconductors

    What is the meaning of zero resistivity in superconductors? I mean, what's the cause of zero resistivity in superconductors?
  42. R

    Some questions on superconductors

    Here are some questions on superconductors that I would like ask- The first one is What are the differences between superconductors and infinite conductors?
  43. N

    D-Wave Superconductors: Definition & Explanation

    Hi I've been searcing the WWW, but I can't seem to find an exact definition of a d-wave superconductor. Is a d-wave superconductor simply a superconductor, where the Cooper pairs are formed by d-shell electrons?
  44. N

    Superconductors and quasiparticles

    Hi I read on Wikipedia that a broken Cooper pair is called a Bogoliubov quasiparticle (source: http://en.wikipedia.org/wiki/Quasiparticle). Is that really true (if yes, then is there a difference between QPs in a metal and a superconductor)?
  45. L

    Significance of delta in oxygen component of superconductors

    Various chemical formulae for the composition of superconductors quote the oxygen content, ie the number oxygen atoms present, as say Osub(10-delta). I would like to know the significance of delta.
  46. N

    Superconductors and Fermi surfaces

    Hi The dispersion of Bogolyubov quasiparticles in a d-wave superconductor is E(\mathbf k) = \pm \sqrt{\varepsilon (\mathbf k)^2+\Delta (\mathbf k)^2}, where ε(k) is the normal-state dispersion and ∆(k) is the gap dispersion. My question is: The Fermi surface (FS) of the normal...
  47. N

    Exploring the Contradiction of Non-Interacting Fermions in Superconductors

    Hi In superconductors, the fermions are interacting. In order to diagonalize our Hamiltonian (which contains the product of four fermion operators), we use Wick's theorem to approximate the product of four fermion operators by the product of two fermion operators. Now, a Hamiltonian...
  48. R

    Calculating Electron Movement and Energy in Superconducting Loops

    Say you have a superconducting loop of copper. If there's an increasing magnetic field through it that induces an E field around the loop, how are the electrons moving when the field stops increasing? As I understand it the current is preserved. Is there some way to calculate the energy...
  49. G

    What's up with spinning superconductors?

    Years ago they showed on TV, that spinning superconductors sort of shield gravitational field. Now I read http://news.softpedia.com/news/The-First-Test-That-Proves-General-Theory-of-Relativity-Wrong-20259.shtml How serious is this to be taken?
  50. C

    Some questions on properties of superconductors

    Hi all, I was wondering if someone can explain to me whether: 1) Superconductors are attracted to originally unmagnetised ferromagnetic or paramagnetic materials? AIUI superconductors are perfect diamagnets due to the Meisnner Effect, and magnetic attraction is due to the creation of...
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