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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Temperature versus disorder phase diagram of Iron pnictides superconductor

Coexistence of magnetism and superconductivity is one of the chief feature in Iron pnictides. I have been trying to reproduce the phase diagram given in upper panel of fig1 in the journal published in ...
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Does Cooper pairs only flow at surface at $T=0\rm K$? Then, how about at the temperature above 0K?

We know that Cooper pairs generate at critical temperature, and as more as reducing the temperature. But where are they? We also know them exhibit around Fermi surface as the wave-function. So, it ...
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BCS theory without breaking symmetry?

I'm studying the analogies between the Higgs mechanism and superconductivity, specially, the BCS theory. To develop the BCS theory, a mean field aproximation is done, which breaks the gauge invariance....
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Gapless superconductivity

I don't understand what is meant by "gapless superconductors". As far as I know, the superconducting gap is necessairy for both zero resistance and the Meissner effect, the two hallmarks of ...
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Shielding by superconductive sphere layer (cavity)?

Does a superconductive sphere layer (cavity with vacuum inside) remove from its interior both, (external) electrostatic and magnetostatic fiels? I imagine a high-frequency field can enter, because of ...
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Can light or any other electromagnetic wave travel through a superconductor?

We know that light is an electromagnetic wave, so it depends on the permittivity and permeability of a substance. The permittivity and permeability of free space(vacuum) are constants. So, propagation ...
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Opposite currents in adjacent superconductors

I understand that the maximum current that may be carried in a superconductor is limited by the magnetic field the superconductor is in, which is very often almost exactly the field generated by the ...
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In a superconducting ring, why are the shielding currents in opposite directions?

In this photo you see on the right-hand side that the outer wall current is negative and the inner wall current is positive. That is, they are directed in different directions. But if the applied ...
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Deriving London Equation from Helmholtz energy

I'm trying to derive the London equation of superconductivity following the book Ginzburg-Landau Phase Transition Theory and Superconductivity. So I arrived to: \begin{gather} \mathcal{F} = \mathcal{F}...
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Excitation spectrum in BCS theory and mean field theory

I've recently been learning about the BCS theory of superconductivity. An extremely rough idea is as follows: given the interacting BCS Hamiltonian $$ H = \sum_{\vec{k}\sigma} \xi_{\vec{k}} c^{\dagger}...
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Kinetic Inductance and Magnetic Flux

Superconductors are known to have kinetic inductance which is the manifestation of the inertial mass of superfluid. In this link, the concept is explained as follows: When a current flows the ...
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BCS state with finite current

How is the BCS state and associated BdG quasiparticle hamiltonian altered by the presence of a finite current? Is there a standard text where this is discussed? (I didn't see anything in Altland and ...
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Cooper pairs and superconductivity

This might be a dumb series of questions, because I'm not a theoretical or condensed matter physicist. If there was a method of pairing all electrons before entering a semiconductor, would you ...
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Paramagnetic current density operator in second quantization

I'm reading Tinkham's Superconductivity book and I don't see how Tinkham obtained the following expression for the paramagnetic current density operator (eq. 3.100): \begin{equation} J_1=\frac{e \hbar}...
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Kernel in Tinkham's Superconductivity book

I'm reading Tinkham's superconductivity book. I'm having especially trouble with the chapter "electrodynamics". I don't see how Tinham went from the equation below "current density $J_1(...
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’t Hooft 1982 Phys. Scr. 25 133 on superconductivity

In G. ’t Hooft 1982 Phys. Scr. 25 133 paper 'The Topological Mechanism for Permanent Quark Confinement in a Non-Abelian Gauge Theory' He wrote in the abstract: We first argue that indeed ...
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Superfluid + Super conductivity in a bose condensate

so my question is this can we theoretically and empirically find a BOSE condensate, with SUPERFLUID properties but which is also a SUPERCONDUCTING device ?
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Bogoliubov- de Gennes Hamiltonian and Anti-Commutation Rule

I encounter a problem which is related to Bogoliubov-de Gennes(BdG) Hamiltonian. Suppose I use BdG theory to transform my many body Hamiltonian into the following form: \begin{equation} \hat{H} = \...
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How do a superconductor and regular current carrying conductor interact?

Electricity tends to follow the path of least resistance, and superconductors have a resistance of 0. So I was thinking that if a superconductor was connected to GND and brought to a normal current ...
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What makes cooper pairs hop to another superconductor?

I know the derivation and how the Josephson effect works. But if we just have two slabs of superconducting material placed together with an insulator between them, what makes the initial hopping occur?...
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Precise Definition of Vortex Halos?

I have read many papers on pair density waves (PDWs) and often time vortex halos are mentioned. These occur when a uniform superconducting component is the dominant order competing with the PDW phase. ...
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Why the electric field inside a superconductor is always zero?

Recently I have been reading the book called "Superconductivity, Superfluids and Condensates" from James F. Annett. I was confused by the expression that zero electric field at all points ...
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How was the superconducting order parameter discovered?

Just wondering if anyone knows the history behind this discovery? The BCS mean field theory suggests a breaking of our $U(1)$ symmetry; hence, a complex order parameter makes sense in that regard. How ...
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Electric currents due to the Coriolis force?

In the Compton generator experiment one uses a hollow glass tube filled with water. When this is flipped over, the water gains a small velocity of the order of 0.1 mm/s for a 1 m radius tube, due to ...
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Hamiltonian in second quantization

I'm reading Tinhkam's Superconductivity book and I'm not able to understand how he ended up with Eq. 3.97. He started with a Hamiltonian $H=\frac{ie\hbar}{m} \sum \limits_i \vec{A} \nabla_i $, used ...
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If there's no electric field inside superconductor, then how could there exist current?

If a superconducting wire has infinite conductivity, then there should be zero electric field inside it. However if there's no electric field inside it, there should be no current (as there's no ...
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What would the Capacitance between a Superconductor Plate & a non-Superconductor Plate?

Assume Plate 1 is Superconducting, and completely isolated(no attached non-superconducting conductor connection) but has a small (nA or $\mu$A) continuous current Assume Plate 1 is separated from ...
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Why do doped Mott Insulators describe high Tc Superconductors

Often people justify research on Mott Insulators / Hubbard model because a "doped" (added impurities) Mott Insulator may be useful in describing high Tc-superconductors like the cuprates. ...
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Normal metal-superconductor action (revealing Andreev reflection)

Short Example A conventional Josephson junction, which consists of a superconductor-insulator-superconductor (SIS) sandwich and is biased by a constant current $I$, has the following action: $$S_{SIS}\...
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How does q superconductor moves along a line of magnets if it's flux-pinned?

So I saw a plenty of demonstrations where superconducting piece of material moves freely along a magnetic surface, usually a line of arranged magnets, and at the same time it is claimed that flux ...
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Particle-hole statistics relation with superconductors

I have a problem regarding the Fermi-Dirac (FD) functions and the relation between particles and hole. The FD distribution for an electron is $$ f^e(\varepsilon) = \frac{1}{1+\exp(\frac{\varepsilon-\...
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What would be the maximum critical magnetic field of superconducting hydrogen?

Say you have a superconductor made of metallic hydrogen. What would the be the maximum critical magnetic field? I know that the new superconducting magnets such as YBCO can reach field strengths of up ...
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Is there spin-singlet $p$-wave superconductivity?

Superconductor-proximitized materials with spin-orbit coupling are expected to host $p$-wave superconductivity. In Alicea2010, it seems like that the superconducting proximity induced effective p-wave ...
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Does the theory of holographic superconductors have any application?

I recently became aware of the relatively novel concept of holographic superconductors, and I was wondering whether anyone here has read something about experimental application of these theories. ...
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Resistance of superconductors [duplicate]

Is the resistance of superconductor,in reality, actually zero? Or is it too low (negligible resistance)?
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BCS and Feynman Diagrams

I am currently studying the strong coupling theory (by Eliashberg) of superconductivity, which is derived by BCS by considering self-energy diagrams and the following interaction potential $$ V(q, i\...
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Density states of Cooper pairs

In superconductivity we can treat the electrons of a Cooper pair as a boson and electrons can occupy the same energy level. But for temperatures above $0$ K and below $T_c$ not all electrons will be ...
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Can (anti)ferromagnet be superconductor by proximity effect?

If I put a very thin (anti)ferromagnet between two superconductors, is it possible to become a superconductor via proximity effect? For example, a supercurrent exists with zero voltage drop.
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How does too much current 'kill' a type-2 superconductor?

I recently saw this post: Can a superconducting wire conduct unlimited current? One of the responses mentioned the Meissner effect. However, I am aware that this occurs primarily in type-1 ...
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Ginzburg-Landau and Coherence Length

Consider the Ginzburg-Landau functional for a complex function $\psi:\mathbb{R}^3 \to \mathbb{C}$, i.e., $$ F[\psi]=\int \frac{1}{2M}|(-i\hbar\nabla -eA)\psi|^2+r|\psi|^2+\frac{u}{2}|\psi|^4 + \frac{B^...
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BCS theory energy gap

I am studying BCS theory of superconductivity and have understood everything except this part: According to HyperPhysics "The electron pairs have a slightly lower energy and leave an energy gap ...
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How is the BCS ground state a coherent state?

A coherent state is defined as the eigenstate of the annihilation operator $\hat{a}$. It can be obtained from the vacuum of the number operator by acting with displacement operator: $$|z\rangle=\hat{D}...
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Resistance in superconductor with quasi-particle

If current is applied to a superconductor with quasi-particles, that is an excited superconductor, will the voltage be measured within the superconductor? In my opinion, when the current is applied, ...
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Holographic and BCS Superconductors

The AdS/CFT correspondence can explain superconductors in a holographic way, using bulk gravity with a black hole in the background and a scalar field which, under suitable conditions, acquires a VEV ...
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Energy of Cooper pairs

Which is the energy of one Cooper pair? Is it below some energy bands (1s,2s) since a Cooper pair is a boson ?Which is the ground state of a boson (electron -phonon-electron)?
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Draw Cooper Pairs in a band diagram

How can we draw a Cooper pair in a band diagram? Can we draw a Cooper pair in a band diagram? I know that Cooper pairs have very small energy (because they obey the Bose-Einstein statistics) but I was ...
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How to measure critical current of a superconducting wire, if my current source can only supply a small current?

I need to determine the critical current of an aluminum wire at 0.1Kelvin. I have access to dilution fridges, but I cannot modify the wiring in the system from room temperature to the sample space. ...
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Thermal conductivity of superconducting material

I design a thermal management system. I came across the idea that superconducting material (at the proper temperature) can be used as a perfect heat conductor. My question is "Do superconducting ...
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Conceptual doubt in Superfluidity

I'm trying to understand superfluidity from these Caltech notes on Advanced Statistical Physics (Week 1, Section IV: Landau Criterion for Superfluidity) - So far it is not clear why a moving ...
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Has anyone measured Flux Friction for different materials?

I was reading this question: What happens when a force is applied to a flux pinned superconductor? And the answer to it basically suggests that for a flux pinned object to move it from some physical ...

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