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 the “BCS Cooper pair condensation” as a physical phenomenon in terms of experiments?

"Thought" experiments and "numerical" experiments are allowed. This question is motivated by the question Has BCS Cooper pair condensate been observed in experiment? , and by our recent research on ...
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Superconductivity in graphene with spin orbital coupling, is it proper to let the order parameter on two sub-lattice equal?

I am reading this article: Edge superconducting correlation in the attractive-U Kane-Mele-Hubbard model. Considering just the first part of the article, where a negative-U Hubbard model with the ...
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How do photons decay in superconductors?

If $A$ is the vector potential, the London equations imply that: $$(\nabla^{2}-\mu^{2})A=0$$ if there is no external current. This can be interpreted as an effective photon mass and so, light ...
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316 views

What is the meaning of Non-Relativistic theory in Condensed Matter Physics?

I an attempt to evade the Goldstone Theorem, it is argued in Gilbert and Klein and Lee's paper that in a non-relativistic field there exists a preferred direction which can be used to evade ...
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230 views

Superconductor general concept questions

I was thinking about building an electric motor using superconductors and I have some general concept questions in regards to how the behavior might be different from ordinary wires. The Meissner ...
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127 views

How can Superconductivity materials levitate permanent magnet?

I have thought that by eddy current. But how eddy current in superconductivity materials can be generated by using permanent magnet?
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Why is the AdS/CFT approach to superconductors rarely cited in condensed matter publications?

Let me put things into perspective by comparing with other applications of string theory. Nowadays review papers written by cosmologists about inflation models often discuss string theory scenarios ...
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Is the uniqueness theorem correct in superconductivity?

There is an uniqueness theorem in electromagnetism. It says that the solution of Maxwell's Equations is determined uniquely by boundary conditions. We can treat superconductivity as a completely ...
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Why is there a Majorana zero mode in the $\pi$ flux core of the p+ip superconductor?

In this review paper (http://arxiv.org/pdf/1202.1293.pdf), the author shows that threading a $\pi$ flux through a 2D $p_x+ip_y$ superconductor will trap a Majorana zero mode at the flux center. The ...
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How does Cooper pairing work?

Cooper pairs are one of the models how superconductivity is explained. What still baffles me is how a vibration of the crystal lattice (the so-called phonon) can interact with the electron (an actual ...
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What is meant by the quantum integrity in a superconducting loop

I encountered this in the context of using squid microscopy to test for d-wave pairing in an iron arsenide superconductor where the goal of the experiment was to detect half integer flux quantum ...
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Bogoliubov - de Gennes Hamiltonian and Zeeman energy

For my system I can write down the Hamiltonian in this form: $$ H = \begin{pmatrix} \epsilon_{1\downarrow}-\mu_{B}B & 0 & 0 & 0 \\ 0 & \epsilon_{2\uparrow}+\mu_{B}B & 0 & 0 \\ ...
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Qubit in Type 1.5 superconductor?

I'm interested in Type 1.5 superconductors, first proposed by Egor Babaev in 2002 and found in the laboratory in 2009 (magnesium dibromide). Such conductors favor small bundles of vortices. The most ...
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Does Fluctuation-exchange (FLEX) approximation including spin-orbit coupling (SOC) exist?

FLEX method was invented by N.E.Bickers and D.J.Scalapino in 1989 (PRL 62,961; Ann. Phys. 193,206). Later it was extended to multi-orbital system (T.Takimoto,PRB,69,104504). But I don't find FLEX ...
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106 views

Trace of the number operator in second quantization

I would like to find the helmholtz free energy of a system $F=-T ln(Tr[e^{\frac{-H}{T}}])$ namely a bcs superconductor (using Annett's notation) $H=\sum E_k (b_{k\uparrow}^\dagger ...
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generation / destruction of fermions by phonons

my Hamiltonian consists of 1D free fermions coupled to a bosonic bath. The interaction is dictated both by scattering terms $H^{scatt}=\sum_{kq}\alpha^S_{kq}c^\dagger_kc_{k+q}X_q+h.c.$ as well as ...
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Can flux pinning be used for propulsion in Earth's magnetic field?

I was wondering if the following steps would result in a net displacement on a spacecraft operating in Earth's magnetic field: Turn on a superconductor Use a linear actuator to shift some mass Turn ...
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66 views

Current between supeconducting rings

How to calculate the current between two superconducting rings with radius r separated by a distance d? Please note that being unfamiliar to the concept of superconducting rings, I can't approach ...
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40 views

What is the status of the Gennes - Alexander theory of Superconducting Micronetworks?

I have started reading the book Connectivity and Superconductivity which gives an introduction to the ideas of de Gennes-Alexander theory. My question is: how is this theory regarded experimentally? ...
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A single valued function from a multi-valued function

In Schrieffer's book "Theory of Superconductivity", there is said when he deals with multiple connected superconductors (and discuss London equations), that if one takes the line integral of the ...
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38 views

How Does The Macroscopic Wavefunction Build Up?

How does the macroscopic wavefunction (the order parameter) builds up from zero value to the a finite value when liquid He undergoes a transition from normal to the superfluid state? How does it ...
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22 views

Superconducting loop as a particle detector?

Imagine that one has induced a persistent current in a superconducting loop. If a particle interacted with an electron in one of the Cooper pairs then would some decoherence and dissipation occur? I ...
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Drift velocity of electrons in a superconducting loop

Do electrons travel at the Fermi velocity in a superconducting loop? For metals the Fermi velocity seems to be around $10^6$ m/s. So would electrons (in a Cooper pair) travel around the loop at this ...
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35 views

Superconducting wire in a Magnetic Field?

A superconducting wire($SC$) is moved rapidly in a magnetic field( $1$ $Tesla$), what would happen to the wire? Are there any forces induced of attraction or repulsion? In a typical conductor, we ...
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45 views

Falling to closest quantized circulation level in a rotating superfluid

To make a superfluid rotate in an annulus shaped container, we start with a normal fluid, rotate the container, then cool it to below critical temperature to get a rotating superfluid. The allowed ...
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29 views

Josephson effect - fractional or not

It is well known that a current proportional to $J\propto\sin(\phi_1-\phi_2)$ flows when two superconductor with phases $\phi_1$ and $\phi_2$ are connected. Also, a current which depends on the ...
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Why supra-conductivity became super-conductivity?

The original article by the Kammerling Onnes team in Leiden does not give a name to the new effect: Kammerling Onnes, H. Further experiments with liquid helium. C. On the change of electric ...
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Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
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what are the main factors holding back magnetic energy storage systems?

Perhaps is it the magnet's own magnetic field that causes it to lose its superconductive state? It seems as though these systems could become incredible energy dense.
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Some questions about the edge states for time-reversal invariant topological superconductors?

Stimulated by my some recent calculations on edge states(ES) for time-reversal invariant(TRI) topological superconductors(TS) as well as many questions concerning the "edge states" in Physics ...
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59 views

Single electron pumps, superconducting energy gap

I am seeking to find out how many electrons per gate cycle are pumped at different temperatures. The Single Electron Pump is made out of Al, with a $T_c=1.2\,\mathrm{K}$. This single electron pump is ...
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30 views

Commutators of differential and field operators

In $p+ip$ superconductivity, a term in the Hamiltonian (in polar coordinates) is $$ H=\int \mathrm{d}^2\vec{r} \left[ \left( \partial_r -\frac{i}{r} \partial_{\theta} \right) \psi^\dagger(\vec{r}) ...
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Numerical solution of the BCS gap equation, with Coulomb potential

I'm interested in the excitons condensation, which is described by an equation which is very similar to the standard BCS gap equation. I will be referring to this article: ...
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Reference for Correlation Lengths of various superconducting materials

Is there a standard reference in which one would look up the experimentally determined correlation lengths $\xi_0$ for various superconducting materials? This is often called the intrinsic coherence ...
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Does the presence of atoms hinder current flow?

When current flows through a material, electric resistance is observed when the electrons collide with the material's vibrating atoms. My textbook says that when we cool the material till the point ...
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Acting on a current density operator in second quantization

I have a current density operator in second quantization in the form: $\hat{J} = -i\left(\psi^\dagger \partial_x \psi - (\partial_x \psi^\dagger) \psi \right) $ operating on some state: $|\phi ...
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Can I generate electricity through superconductors?

Can a superconductor produce electricity in any condition or in any state? OR can it be used to produce electricity with the help of any other components?
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Most efficient (superconductive) coil design for generating inductance

What is the most efficient coil geometry for a magnet. I am assuming that toroidal coil are ultimately the most efficient as they are mechanically less susceptible to becoming destroyed. Are any sort ...
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Quantum Locking - Scale Up

In the conversation on QL, it mentions that the flux lines occur at the points of imperfection in the crystal(?). So as the material gets thicker, the field cannot penetrate... Would it be possible to ...
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Should we expect reliable nano-particle engines within the next 5 years?

"Regarding engines" what are the current theories and examples of ongoing progress in nanoparticles? References: National Nanotechnology Initiative electric motor made from one molecule 18 atoms ...