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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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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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What is the meaning of the gap energy in superconductor? [on hold]

For superconductors the energy gap is a region of suppressed density of states around the Fermi energy, but I do not understand the meaning of this.
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Calculated SC Solenoid Inductance / Energy Values …Looks Wrong? [on hold]

I am working on a hobby solenoid design project using google sheets/CAD to teach myself more and I'm stuck, my numbers for the coil inductance look wrong, making the energy seems absurdly high. ...
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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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Calculating magnetic field outside the core magnetic field region (split pair superconducting magnet)

In this article, they have calculated fringe field from a split-pair magnet. It seems like the magnetic field strength is decaying exponentially. Which equation would support this kind of decay? ...
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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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How fluctuation superconductivity and granular superconductivity is related? Is the same?

I cam across two terms in superconductivity; fluctuation phenomena in superconductivity and granular superconductivity. I need help in distinguishing between them.
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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 ...
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How many types of phonons are there, and what are their characteristics?

I've skimmed through Wikipedia's article, as well as as PSE question What is a phonon?, but I am still entirely left in confusion as to the types of phonons and their corresponding characteristics and ...
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Is the Bogoliubov quasiparticle boson or fermion?

The Bogoliubov quasiparticle combines the properties of a negatively charged electron and a positively charged hole, so here we have two fermion and the quasiparticle have an integer spin. By this ...
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What is the point in discovering a material that is superconductor at very low temperatures?

From my understanding what is really relevant is to obtain superconductivity at high temperatures, as close as possible to standard conditions of pressure and temperature. So, what makes materials ...
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Tunneling junction in electromagnetic field [closed]

Why in presence of electromagnetic field hamiltonian,describing 2 systems with tunneling(for example josephson junction ) $$H=H_L+H_R+T(I+I^{\dagger})$$ where $I=c_Lc^{\dagger}_R$ is tunneling ...
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Using superconducting coils as a transformer

In experiments such as tokamaks, typically an ohmic transformer (primary) is used to produce current in the plasma (secondary) by swinging from to the most positive to negative magnetic field. Ideally ...
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Ginzburg-Landau boundary condition in the 1D no fields case

It is commonly seen that in finding the coherence length from Ginzburg-Landau, that the following equation is found: $\frac{\partial^2 f}{\partial \eta^2} + f(1-f^2) = 0$ which is for a superconductor ...
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Equation for kinetic inductance and the Mattis Bardeen Formula

I've been reading Tunable superconducting nanoinductors by Annunziata et al. 2010 which is a paper in which they construct inductors from ultra-thin, approximately 100 nm wide strips of niobium (Nb) ...
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the origin of flux pinning force in mixed state of a superconductor

The flux lines tends to get pinned at the imperfections present in the material, called as pinning centres. But what is the origin of that pinning force, which holds the flux lines at such sites
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The free energy expansion in terms of order parameter in GL theory

Please check the image provided. If somebody can explain why the last two terms were considered and how it happened to be so. According to some text books, its because of expulsion of applied field by ...
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Formulating BCS theory in the functional integral with a real order parameter

Often in BCS theory, people take the order parameter $\Delta$ to be real. I tried to construct a BCS theory with a real order parameter from the start and ran into some trouble. I'd be interested to ...
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What “transformations” did Abrikosov use in 1958 to get the famous $11-2\log{2}$ result in fermi-liquid theory?

How does one obtain the final integral expression in the appendix of Abrikosov and Khalatnikov's 1958 paper: $\ \ \ $ "Concerning a model for a non-ideal fermi gas" $\ \ \ $ ??? Below, in Bold, I ...
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Metallic state in 2D

Mermin Wagner theorem prevents any spontaneous breaking of continuous symmetry for short ranged interactions for dimensions, D $\leq$2 for any finite temperature. So I understand that superconducting ...
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Why do microwave ports for superconducting qubits look the way they are?

Often you see input/output ports for superconducting qubits looking like this block, which tapers down to a narrow transmission line: what is the reason for this tapering, and how do you actually ...
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Does the penetrating magnetic field lines affect the Eddy currents cancellation of an exterior magnetic field?

If a Type-II superconductor's surface is placed near a resistive wire, and current($I$) is applied, during a short duration of time while the current is reaching steady state, the magnetic field of ...
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Current-current correlator in superconductivity

I was reading a paper on superconductivity. There is a claim that if the momentum space current-current correlation function $\langle\mathcal{T} j_{\mu}(k)j_{\nu}(-k) \rangle$ has a pole at zero ...
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Is there any complete list of all discovered superconductors since the discovery?

There are many reported superconducting materials since discovery. I am looking for a database/paper/review article incorporating all the materials that are reported as superconducting. Is there any ...
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Vortex motion in superconductors

In mixed state of a type-II superconductor, when we allow a transport current to pass through it, we say that the Lorentz force acts and as a result the flux starts flowing, when the force is greater ...
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band gap (or energy gap) relation with discontinuity on spceific heat

Is change in band gap or energy gap with respect to temperature, reason behind the discontinuity in specific heat data as in case of superconductors?
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Current-current correlation function and stiffness constant for BCS problem

The BCS Hamiltonian after doing appropriate mean field decomposition of the quartic interaction term is, $ H=\sum_{k,\sigma} \zeta_{k} c_{k\sigma}^{\dagger}c_{k\sigma}-\sum_{k}(\Delta_{k} c_{k\...