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 theory describes high temperature superconductivity more sucessfully?

We know that there are so many theories on the high temperature superconductivity in cuprate. E.g. the U(1)/SU(2) gauge theory description of doped Mott insulator[Lee, Nagaosa, Wen], the phase-string ...
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What is the Difference Between a Type-1 and a Type-2 Superconductor?

As the title says, I was wondering what the difference was between a Type-1 and a Type-2 Superconductor. Especially in terms of the Coherent Length and Penetration Depth of a Magnetic Field - and how ...
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741 views

What is the Difference between a Lepton and a Fermion?

As the Title Says: I am Wondering what the Difference between a Lepton and A Fermion is. I know they both have an ½ integer spin number e.g. a electron, an atom with an odd mass number such as ...
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What happens to a superconductor when a magnetic fields strength increases?

I'm curious about what happens when a HTS is locked in place above a magnet via the Meissner Effect and say another magnet is added. Would the superconductors height fluctuate? Or would the extra ...
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What is the Difference Between BCS Theory and Ginzburg-Landau Theory?

What is the Difference Between BCS Theory and Ginzburg-Landau Theory? I have been studying Superconductivity and I know that Both of the theories (BCS Theory and Ginzburg-Landau Theory) can be used ...
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Origin of High-temperature Superconductivity

What is the mechanism that causes certain materials to exhibit superconductivity at temperatures much higher than around 25 kelvin?
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Rigorously prove that electric field is zero in a perfect conductor

I have ran into a problem while trying to prove that the electric field is zero in a perfect conductor My argument went something like this: We know that: $$\vec J = \sigma \vec E$$ In a ...
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43 views

Wave function of N electrons in a superconductor

Assuming that the wave function consisting of $N$ electrons is $\Psi_{N}(\bf{r_1,r_2,\cdots r_N)}$ then in the presence of a magnetic field ($\bf{B}=\nabla \times A$), how do I show that the current ...
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Nature of Cooper pairs

Some people say it is bound state, some say it is not. Which is more accurate? Problem is that I read in some books, including Ziman, that Cooper pairs are bound states but my teacher says that it is ...
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Why does Pressure Increase the Tc (Critical Temperature) of a Superconductor?

Just a heads up - please make this answer understandable to around 1st year degree level physics - not PhD research. So I can understand it - thanks. I was wondering why they Critical Temperature ...
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1answer
40 views

Introducing time-dependent drive into the Hamiltonian of quantised electric circuits

Suppose I have the schematic of a superconducting electric circuit composed of (quasi) lossless linear inductances and capacitances and some non-linear inductances, eg. Josephson junctions. The ...
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Why is the fermi surface of electron higher than the surface of hole in Iron-based superconductors?

I think the hole is higher than the electron in the brillouin zone, but the results of some experiments, like the ARPES, show the opposite results, why?
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How does current flow in superconductors if Cooper pairs have zero momentum?

I've been reading a lot of condensed matter textbooks, which state both that the net momentum of a Cooper pair in a superconductor is zero, and that Cooper pairs have momentum when they carry current. ...
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Real part of the AC conductivity has a discrete spectrum => What physics?

If the real part of the AC conductivity $\text{Re}[\sigma(\omega)]$ has a discrete spectrum only, i.e., $\text{Re}[\sigma(\omega)]=a_1\delta(\omega-\omega_1)+a_2\delta(\omega-\omega_2)+\cdots,$ what ...
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53 views

How to generalize BdG equation in order to match a graphene with a metal superconductor?

I want to generalize BdG equation in order to compute the conductance of a junction of graphene with a metal superconductor. The previous works done until now on this hetrojunction is devotted to use ...
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88 views

To what extent can the superconducting order parameter be thought of as a macroscopic wavefunction?

I know that the order parameter does not obey the Schrodinger equation; it instead obeys the Ginzburg-Landau equation. However, I am unclear as to the situations under which the view of the ...
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1answer
65 views

Superfluid rotating frame of reference

I'm currently studying a text about Bose-Einstein condensates (BECs) and vortices. When they want to study whether a vortex will be formed, they look at the fact wether it's enegetically favorable. ...
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50 views

Ampère's law and superconductors

I have been reading about superconductors and emerge me a inquietude about the explanation of existence of currents inside the superconductor while their magnetic field (inside too) is zero. Based in ...
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Does a superconducting state change in a Type 2 collapse the whole superconductor?

If (say) we have a 1m length bar of a Type 2 superconductor in a superconducting state and something is done to one end of it to collapse the superconduction there, does the state of the whole bar ...
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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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2answers
40 views

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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70 views

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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91 views

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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106 views

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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56 views

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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47 views

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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83 views

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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21 views

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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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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469 views

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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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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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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213 views

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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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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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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281 views

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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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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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 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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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 ...