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Questions tagged [superconductivity]

Superconductivity is the transmission of current with no resistive losses, and is one of the most active areas of condensed matter physics research.

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What is clean limit and dirty limit?

In superconductor there has two limits, one called as clean and other one called dirty limit. But what are that meaning? What means clean and dirty? How the coherence length depends on the electron ...
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Aluminum critical current vs temperature fit

I have some data at different temperatures of Al's critical current (from 600 mK to 1.5K). Tc of Al is ~ 1.3. I am now trying to fit this data to a model to extract the theoretical critical current ...
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Does superconducting magnet prevents energy loss when hadron is being accelerated?

I read up on how synchrotron works and electron will heats up by emitting photon when it is steering(accelerating) around a bend, so more bends more heat loss. By heat I mean energy not necessarily ...
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About Supercurrent Direction in London Theory of Supercondutivity

I'm studying superconductivity starting from London's approach. After you obtain the two London's eqs you get for the static case: $\quad \nabla^2 \textbf{B}=\frac{1}{\lambda_L^2}\textbf{B}$ If ...
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Perpendicular field dependence of the superconducting energy gap in thin films

I'm looking for an expression for the perpendicular field dependence of the superconducting energy gap $\Delta$ in thin films. What I mean by this is the analog to what is described in the Ginzburg ...
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How does a super current affect ductility, maleability and the mechanical properties of a superconductor?

In metals, the ductility, malleability, tensile strength and strain are all determined in part by their free electrons. I am wondering what would happen to all of these properties of a superconductor ...
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Hall effect in superconductors

In many papers on Hall effect in superconductors (in the mixed state), experimental results are plotted as magnetic field vs Hall angle. Why we need to consider the Hall angle in these cases? Can't we ...
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Why can't we have superconductors?

My book says, "Short circuiting occurs when the live wire comes in direct contact with the neutral wire, so a zero resistance path is provided to the current. A heavy current then passes through the ...
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Meissner effect

Meissner effect Why do field lines again get back to straight line after getting deflecting during superconducting state?
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BCS theory for neutral fermions

As I understand it, Cooper pairs form between two fermions and are the cause of superconductivity. I was told by a teacher that the formation of Cooper pairs and BCS theory requires both fermions to ...
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Charging of a superconducting island for arbitrary junction transmission

For this question I am considering a system much like the traditional Cooper pair box shown below: we have a superconducting island, capacitively coupled to a gate electrode, and coupled to a ...
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Superconductive magnet as a source of energy?

Could we charge a superconductive magnet and use it as a source of energy?
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Is there an magnetic field around ideal conductor?

Im gonna dive straight to the point: If you run some current through, say, copper wire you will get a magnetic field around it; that is how the gauss guns work. My questions are: 1) Is it possible ...
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Can superconductivity be understood to be a result of quantum entanglement?

I've been trying to find out what causes superconductivity. I have seen a lot about what characterizes it (e.g the Meissner effect). But I haven't found much on the root cause. The closest I have ...
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What would happen if a Type 1 superconducting sphere was placed over the north pole of a magnet?

This is a bit of a thought experiment but I thought it was rather interesting. I was doing research on superconductivity of Type 1 materials and how they repel magnetic flux due to the Meissner effect....
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Importance of Relative Grain Alignment in High Temperature Superconductors for High Current Applications

I'm currently studying superconductivity, and am attempting to work through a sample paper as exam preparation. Unfortunately, the lecture notes provided aren't of the highest standard and in certain ...
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Treating $-E_J \vert{\cos{(\hat{\theta}/2)}}\vert$ in the charge basis

I'm trying to write down the Hamiltonian for a Cooper pair box in the charge basis in the scenario where the Josephson potential term is not $-E_J \cos{\hat{\theta}}$, but $-E_J \vert{\cos{(\hat{\...
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Hydrogen Sulfide New Superconductor? Is It Possible For Hydrogen Sulfide?

According to a very trusted science source : https://www.zmescience.com/science/news-science/superconductivity-artic-temperatures-05342/ There is now such thing as a Hydrogen Sulfide Superconductor ...
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Temperature-pressure plot for superconducting records?

Eremets et al. (arXiv:1812.01561) and Hemley et al. (arXiv1808.07695) have reported new high-temperature record for superconductivity, as covered by MIT Tech Review and Physics Today. Not ...
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Would there be any current if an electric circuit is cooled to absolute zero?

My question is if I got a superconductor and cool it to absolute zero at least measurable by today's tool, it should have no electrical resistance but then would there be any current when there is a ...
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Tight-binding extended attractive Hubbard model for unconventional superconductivity

BCS theory suggest that the effective attraction between two electrons, due to electron-phonon coupling, is in momentum ($k-$)space. However, in literature, (real space) tight-binding Hubbard model ...
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Magnetic field of a rotating superconductor - exists?

On several places (e.g. wikipedia superconductivity) people stay, that for superconductivity the resistance is exactly zero. The mass of electron is small, but for sure not exactly zero. Imagine a ...
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What is 'Peak effect' in superconductivity?

I came across a phenomenon in type II superconductors called the "peak effect." To be a little more specific, it has something to do with delocalised vortices. I don't really know what is it all about....
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How is current in superconductors increased microscopically?

Imagine a superconductive ring with its current being increased by EM induction. How is current increased microscopically? I see only two possibilities: ...
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In superconductivity, does the diameter of the cable affect the current?

In the water tank analogy below, the smaller diameter pipe (B2) will drain tank A slower than the larger diameter pipe (B1) We are told that resistance has this same effect on current the bigger the ...
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Inductance in Superconductors

This is a picture I got from a question in this website, it seems totally fine, but if you try looking it gain, is the heater placed in the wrong position? Because as I know current takes the path of ...
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Does a battery 'excites' current to flow in a superconductor? [duplicate]

If yes, how is it possible since a closed circuit with no resistance means 0 voltage, how does the electrons flow initially if there's no potential difference? Any simple explanation or analogy would ...
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About the symmetry of interaction matrix element in superconductivity

In Sigrist, M. & Ueda, K. Phenomenological theory of unconventional superconductivity. Rev. Mod. Phys. 63, 239–311 (1991). There is equation 2.1 write as below $$H = \sum\limits_{{\bf{k}},{\bf{s}}...
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What are Cooper pairs in superconductivity? [duplicate]

At low temperature how does electron become Cooper pair and why can they pass through a superconductor without resistance? Please give quantum mechanical explaination.
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Why don't we have a “Cooper pair” of two holes in a superconductor?

The condensate of Cooper pairs is described by a complex scalar field (or the order parameter) which, when quantized can give rise (or is capable of creating) two types of quanta with charges opposite ...
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Is the hierarchy of Andreev bound state transmission probabilities fixed?

My question is regarding Andreev bound states and their transmission probabilities. But to make this self-contained, lets quickly recap, for which I will draw from Tosi, L., Metzger, C., Goffman, M. F....
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Do superconducter wires still have low resistance above their transition temperature?

Superconducting wires have almost zero resistance below their transistion temperature. But do they still have resistance better than other wires above that temperature?
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Derivation of BCS condensation energy

Many textbook derive BCS condensation energy as $$\begin{array}{l} {\left\langle E \right\rangle _s} - {\left\langle E \right\rangle _n}\\ = \sum\limits_{\left| {\bf{k}} \right| > {k_F}} {\left( {...
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Why is it that all metals do not become superconductor by lowering the ambient temperature?

Aluminium becomes a superconductor at a temperature below $1.91$K. But I am quite certain that all metals do not exhibit superconductivity even when the temperature is lowered to nanokelvin or below. ...
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Why does type-I superconductor behave differently than type-II as $H$ is increased?

As one increases the external magnetic field $H$ above a critical value $H_c$, a type-I superconductor abruptly changes to a normal conductor. But for type-II, the transition is not sharp but gradual ...
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Why does the bulk of a superconducting material expel magnetic field but not that of a perfect conductor?

It is well-known that when a superconductor (SC) is cooled below the transition temperature $T_c$, the magnetic field passing through the bulk of the SC is completely expelled. In Zee's book on ...
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What is fluctuation superconductivity? What is fluctuating here?

According to larkin "Phenomena which cannot be described by the quasiparticle method or by MFA are usually called fluctuations" . I want to what does he mean by 'Phenomena' here? and in general what ...
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Phase gradient, vector potential and current in a superconductor

For a superconductor we may write a wave function $\psi$ as a function of a density $\rho(\vec{r})$ of particles as $$\psi(\vec{r})=\rho^{1/2}(\vec{r})\,e^{i\theta} \, .$$ This leads to the ...
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Vanishing of Coulomb blockade/charge dispersion in high transparency Josephson junctions

I was recently reading the paper Coulomb Blockade in Superconducting Quantum Point Contacts by Averin from 1999 (see here for the ArXiV, here for the PRL). In here he discusses a peculiar phenomenon:...
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Rest frame of massive photon in Meissner–Ochsenfeld effect

The Meissner–Ochsenfeld effect together with spontaneous symmetry breaking and the London Equation yields $(\Box+M^2)A^\mu=0$ and gives photon an effective mass $q\sqrt{\frac{n_c}{m_c}}$ Which is ...
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How is a superconductor maintaining a persistent current a reversible process?

Once an electric current is established, and then the external electric field/voltage is withdrawn, a superconductor maintains the current forever. Such a process neither violates the first law nor ...
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How is Meissner effect consistent with the frozen field lines inside the superconductor?

From Meissner effect we know that the magnetic field $\vec{B}$ is zero inside the superconductor. Since $\vec{B}=0$ inside the superconductor (ignoring the tiny penetration effect for the moment), ...
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What is the drift velocity of an electron in a superconductor?

How is it,when compared to drift velocity in a conductor?
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How self consistency condition works for a superconductors which is finite and does not have periodic boundary condutions?

So if a superconducting system has periodic boundary conditions the s wave superconducting order parameter calculation by self consistency condition is pretty straightforward. However what if I have ...
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If I apply a position dependent temperature gradient to a s wave superconductor, would I get a position dependent superconducting order parameter?

What would happen if a s wave superconductor placed in a position dependent temperature gradient, where $T(x)<T_c$ is always satisfied. Would I get a position dependent superconducting order ...
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Why a superconductor expel magnetic lines of force from inside completely when cooled below critical temperature?

Suppose a superconductor which is in a normal state (i.e. $T>Tc$) is subjected to a magnetic field. As soon as magnetic field switched from 0 to some value, eddy currents will develop on the ...
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Are Kondo insulators topological insulators? What are their relationship to superconductivity?

Reading about the Kondo effect and Kondo insulators, I found they are strikingly similar to topological insulators. Are Kondo insulators topological insulators? Related question, due to their ...
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Does zero resistance mean that there are no energy exchanging processes between particles in superconductor? [closed]

I was just knowing little bit about bose einstein condensate then I came across superconductor. In the bose einstein condensate particles have same energy levels and they can not escape the level or ...
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Transmons and cooper pair box qubits: two islands or a single island and a reservoir

In scientific literature, one typically describes Cooper pair boxes as a small superconducting island coupled to a superconducting reservoir (say, a large ground plane of superconducting metal, or a ...
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Faraday's law superconducting [duplicate]

When we say flux can't be changed through superconducting coil , because resistance is zero , So this implies there is no induced emf in the coil , If it is so what makes current flow in the coil ...