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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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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Bogoliubov quasiparticle current

How to calculate the quasiparticle current density starting from bogoliubov - de gennes equation: $$\left( \begin{array}{cc}H_{0} - E_{F} & -i\sigma_{y}\Delta \\ i\sigma_{y}\Delta^{*} & E_{F} ...
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How is Meissner effect explained by BCS theory?

Someone says we can derive the GL equations from BCS theory, which can explain Meissner effect, but I want a more clear physical picture of this phenomena.
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Odd-frequency pairing

What is so interesting in odd-frequency pairing in superconductors (Tanaka) ? Why is it worth exploring both theoretically and experimentaly?
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Sign conventions in Devoret Les Houches course on quantum fluctuations in electrical circuits

In this article on p. 364 Devoret writes the "equations of motion" (using KCL) for the electric circuit shown on p. 363. He uses flux instead of voltages. The sign convention he uses, as shown on p. ...
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Looking for a complete review of the BEC-BCS crossover

I'm looking for comprehensive review of the BEC-BCS crossover, both from a theoretical point of view, and from a experimental one. Even something at textbook level, but exhaustive, would be OK, but I ...
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What is the behaviour of this SN interface for $H/H_c$

The SN interface for a Type 1 superconductor looks like this (sorry for bad drawing) Where $x_p = x_s + x_n$. We find $x_p$ to be $x_p = \sqrt{d\delta}/\nu_n \nu_s$. The parameter $\delta$ is just ...
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Why wouldn't a room temperature superconductor violate the laws of physics?

I understand that the laws of physics (as we know them) cannot be violated, but what I would like to know is what I'm missing, because I know there is some explanation that I'm not accounting for. ...
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Ground state of BCS mean field Hamiltonian

I have question following the logics of BCS Theory regarding the ground state. First let me recap the logics of textbooks, for example, by Carsten Timm . After obtaining the interacting BCS ...
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What is the relation between pseudogap and time reversal symmetry breaking?

Some papers concerning high-$T_c$ superconductor discuss the pseudogap and time reversal symmetry breaking. My questions are: What is the characteristic of order-parameter in pseudogap? How to ...
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Superconducting electromagnets?

Is it true that superconducting electromagnets don't need any power? So... energy to created a magnetic field via a superconductor would be zero? Since resistance is zero, does that also mean that ...
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Does a superconductor spinning in a magnetic field radiate?

According to the cyclotron radiation formula: $$ \frac{dE}{dt} = - \frac{\sigma_t B^2 V^2}{c \mu_0 }$$ charges will radiate even when moving perpendicular to the magnetic field (which presumably ...
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Would a portable superconducting coil “battery” be impractical due to magnetism?

I'm working on a science fiction story idea, and trying to make sure I get all of the physics right. One of the concepts I'm using is superconducting coils as "batteries," because they can store huge ...
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Can an analog to the Meissner Effect be proposed for matter and gravitational fields?

In the study of electromagnetic fields and quantum electrodynamics we observe and theorize on the behavior of superconductivity and the Meissner effect. Has an analog of these behaviors been proposed ...
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Magnesium Diboride - why was it missed?

In 2001 it was found to superconduct at 39K, which is about twice the record for materials up until the 1980s when the cuprate high temp superconductors were discovered/invented. My question is ...
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Can superconducting magnets fly (or repel the earth's core)?

If a superconducting magnet and appropriate power supply had just enough $I\cdot s$ (current $\cdot$ length) so that when it was perpendicular to the earth's magnetic field, the force of the ...
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What observables are indicative of BCS Cooper pair condensation?

What observables are indicative of BCS Cooper pair condensation? "Thought" experiments and "numerical" experiments are allowed. This question is motivated by the question Has BCS Cooper pair ...
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What happens when a force is applied to a flux pinned superconductor?

When a force is applied to a superconductor to move it in a direction that it resists because it is flux pinned, where does the additional energy used to overcome the flux pinning resistance go? E.g. ...
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Fractional Josephson effect explained

I am confused by the fractional Josephson effect. I still don't know if there has to be parity conservation or not. Is the fractional Josepshon effect always connected to fermion parity anomaly ...
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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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DC Josephson effect

I was taught that currents are always associated with some nonequilibrium situtations. Now I encountered the DC Josephson effect where equilibrium current can be calculated from this formula: $I = ...
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What kind of free energy do we use for a superconductor in a magnetic field?

My reasoning is as follows (using Gaussian units): Start from the second law: $$dU=TdS+dW,$$ where $dW$ is the work done by the magnetic field. To derive $dW$, we consider a solenoid with current ...
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Equivalence of derivation of Majorana fermions

Perhaps is this a stupid question but I have really no answer. To prove the emergence of Majorana bound states I search zero-energy solution of the Bogoliubov - de Gennes equation $$ ...
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Imaginary Angular Momentum [closed]

I recently came across a problem online where it asks you to interpret an imaginary angular momentum about an axis. Apparently there's a chance it has to do with superconducting. What is the correct ...
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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 to derive electron number equation of Bogoliubov Hamiltonian using thermodynamic relations.

My question arise from this article: Edge superconducting correlation in the attractive-U Kane-Mele-Hubbard model. I will describe my question in detail so that you might not need to look into that ...
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A potential perpetual motion machine?

If I were to freeze a superconductor, the ones made up of yttrium barium copper oxide, with liquid nitrogen and placed it on one of those strong neodymium magnets, it should float right? Now what ...
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A better conceptual model for cooper pairs in a superconductor

The conceptual model I have been introduced to for cooper pairs in a bulk superconductor is what I would call the "wake" model, where one electron deforms the positively charged lattice, changing the ...
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What happens in a circuit, when the wire and the battery are superconducting. And shorted

When a wire with no resistance is connected to the terminals of an ideal battery, will a current exist in the circuit? If a capacitor is added to the circuit, will it be charged by the battery or will ...
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Does the real part of the inverse dielectric function have to be negative at some point for Cooper pairs to form?

Electrons naturally repel one another. However, in a superconductor, a phonon-mediated interaction causes the electrons to have a weak attractive interaction. Suppose that the interaction between two ...
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Particle-hole symmetry and the sign of the superconducting gap

Time-reversal (TR) symmetry leads to topological insulator property. As expected, the topological invariant depends on TR (Pfaffian) operator. TR+particle-hole symmetry leads to topological ...
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Superconductor symmetry breaking

When water freezes continuous translational symmetry is broken. When a metal becomes superconducting, what is the symmetry that gets broken?
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two equivalent forms of BdG hamiltonians?

Consider two Bogoliubov - de Gennes Hamiltonians with equations for excitation energy, $$\left(\begin{array}{cc} H_{0} - E_{F} & \Delta \\ \Delta^{*} & E_{F} - \sigma_{y}H_{0}^{*} \sigma_{y} ...
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Is there Johnson noise in superconductor?

For conductor, the Johnson Noise is $v_n = \sqrt { 4 k_B T R \Delta f }$. It is clear that the noise depends on $R$. I'm curious whether this noise will appear in supercondutor? That is for ...
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Can a super conducting magnet & gravity create a cheap source of energy?

I have a question about whether this would produce a cheap source of energy. If you created two superconductive magnets configured in a figure of eight layout, in a cold enough environment so you ...
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Andreev reflection graphene - metallic superconductor

We have BdG equation, $$\left(\begin{array}{cc} \mathbf{p}\cdot\boldsymbol{\sigma} - V & \Delta_{0}e^{i\phi} \\ \Delta_{0}e^{-i\phi} & V - \mathbf{p}\cdot\boldsymbol{\sigma} \end{array} ...
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Relation between p+ip wave Superconductor and Moore-Read State

I am quite interested in the understanding of the relation between p_ip wave superconductor(SC) and the Moore-Read(MR) state. They share many similar properties, for example, p+ip SC has majorana as ...
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Particle-hole symmetry of Bogoliubov - de Gennes equation

Bogoliubov - de Gennes equation reads, $$\left( \begin{array}{cc} H_{0} - E_{F} & -i\sigma_{y}\Delta \\ i\sigma_{y}\Delta^{*} & E_{F} - H_{0}^{*} \end{array}\right) \left( \begin{array}{c} ...
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Mode-dependent Andreev reflection

Consider the following Hamiltonian which describes massless Dirac fermion on the surface of a topological insulator nanowire, $$H = -i\hbar v_{F}\left[ \partial_{x}\sigma_{x} + ...
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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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How does Ohm's law apply to superconductors?

As radio amateurs we've all learned the various relationships of power, voltage, current and resistance as expressed in Ohm's Law. My question relates to the following simple circuit showing an ideal ...
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Cooper instability

I have a question about the mechanism of Cooper instability. I know the naive picture with two interacting electrons and noninteracting fermi sea wchich leads to the bound state formation. However, if ...
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Why does proximity to a superconductor open a gap in the surface states of topological insulators

I have read in many places that the gapless surface states of 3D topological insulators are robust to perturbations which do not break time-reversal symmetry. I have recently also seen many papers ...
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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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What is the maximum current carrying capacity of a Josephson tunnel junction?

In 1962, Josephson predicted that for a sufficiently thin insulating layer, it should be possible for Cooper pairs to tunnel between two pieces of superconductor. With a potential difference $V$ ...
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Regimes of Josephson junction

There are several formulas to describe critical current in Josepshon S-N-S junction mainly based on Eilenberger and Usadel equations for quasi-classical Green's functions. The starting point is the ...
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Superconductors and magnetic field [closed]

I am working on a project, and I have a question: Concerning superconductors considered as diamagnetic material, what is the equation that describes the repulsive force to a diamagnetic material in a ...
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How to estimate the number of Cooper pairs in type I and type II superconductors, respectively?

When Al (type I) enters a superconductor state ( Meissner state), how many conduction electrons form Cooper pairs, or how many Cooper pairs exist in the Al ( may be number of Cooper pairs / Volume ) ...
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Spin dependent Andreev refelction

What happens with the spin in Andreev reflection process ? The simple Bogoliubov - De Gennes equation for hole and electron does not contain information about the spin. I know there are some ...
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How can we see that there is superconductivity/superfluidity in the boundary theory in the holographic principle?

For example in the models for holographic superconductors we can calculate the conductivity. Also there is an energy gap. I can understand that it describes a superconductor. However I have also heard ...