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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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Origin of Josephson voltage equation?

i cant find a satisfying explanation, and I cant figure it out myself, a derivation for the josephson equation: $$U(t)=\frac{\hbar}{2e}\frac{d\phi}{dt}$$ where $U(t)$ is the voltage, and $\phi$ is the ...
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Symmetric BCS state

The ground state wavefunction for the BCS can be written $$|\Psi_{G}\rangle\equiv\prod_{\textbf{k}}[u_{k}+v_{k}c_{\textbf{k}1}^{+}c_{\textbf{-k}-1}^{+}]|\phi_{0}\rangle,$$ where $|\phi\rangle$ denotes ...
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Superconductivity and phase overlap

Given the following state $$|\Psi^{\phi}\rangle=\prod_{\mathbf{k}}(u_{k}+v_{k}e^{i\phi}c_{k1}^{+}c_{-k-1}^{+})|\phi_{0}\rangle,$$ where $|\phi_{0}>$ is the vacuum, $u_{k}, v_{k}\in\mathbb{R}$, and $...
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How to construct invariant forms under the effect of an arbitrary group?

First I would like to mention that I do not know that should I post this question here or in the math community, but since my background is in physics and this kind of question is usually asked by ...
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Which superconductor does this Hamiltonian describe?

I saw a Hamiltonian for a superconductor somewhere, which I think was of the form $$H = \begin{pmatrix}\nabla-m & \Delta\\ \Delta & \nabla - m\end{pmatrix},$$ but it might be correct only up ...
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Sintering of Yttrium barium copper oxide

I will do an experiment on superconductors, specifically $\text{YBa}_2\text{Cu}_3\text{O}_7$, and I am curios about some steps in the preparation. The starting materials are $\text{Y}_2\text{O}_3$, $\...
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What's the difference and relationship between perfect fluid and superfluid?

Sorry for this naive question, I just cannot find good references talking about the difference and relationship between perfect fluid and superfluid. Could someone explain this to me or point me to ...
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Can we build a superconductor on the Moon and beam energy where needed? [closed]

Should we not build a superconductor facility on the moon ? We find a spot where the rays of the sun don’t provide heat. This should enable a superconductivity facility to operate due to the low ...
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Why in the iron based superconductor interband interaction is dominating?

What is the mechanism of intraband and interband interaction in the iron based superconductor? and Why interband interaction is dominating?
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Relationship between Helium as Superconducting liquid and Phonon

I understand there is critical velocity below which there will be no any Elementary excitation and Liquid will exhibit Super fluidity. But I am unable to understand what decides critical velocity ...
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How do we know that superconductivity is due to Cooper pairs as opposed to pairs of more than 2 electrons?

I am wondering how do we know that superconductivity is due to Cooper pairs? I.e. due to pairing between 2 electrons, as opposed to say, pairs of 6 electrons. If a pair of electrons consists of 6 ...
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Inductance in superconducting wires (and the math)

I'm very curious about inductors in general, and how similar they are to capacitors. In the above picture the formula of current over time in an inductor with wire resistance $R$ is written. I'm ...
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commutation relations when calculating Hamiltonian

I am reading Topics on Superfulidity of Walter Greiner Book Titled "Quantum:Mechanics Special Chapters" In Exercise page no 200, Hamiltonian has been discussed and derived throughly using commutation ...
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What is the Energy of superfluidity helium liquid with momentum hk

I'm reading BK Agrawal Book. In chapter 24, Section 3 and 4 has been given about Interacting fermions and Bosons. Here in 3 Energy of Energies is given directly without any derivation and in 4 ...
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Expression for Superconducting energy gap above the superconducting ground state

Discuss the system of interacting Fermions. Find the expression for superconducting energy gap above the superconducting ground state as $$\Delta = \left[ \frac{2 \hbar^2 k_0 \omega}{m} \right] \...
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Many body BCS theory related question

I am trying to find the mean number of particles in the BCS ground state $|\psi>$, but I am stuck on a step. $$|\psi> = \Pi_{k}(u_{k} + v_{k}c^{{\dagger}}_{{k}{\uparrow}}c^{\dagger}_{{-k}{\...
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Temperature dependency of a superconductor with current

Is there any increase in the temperature of a superconductor when we increase density of current around jc? Is there any related article?
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how is motion possible between a magnet and a superconductor

from my understanding of relative motion between a magnet and a conductor is that eddy currents work to oppose said motion but cannot entirely because of losses in the form of resistance, but without ...
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Would a superconductor act similarly to copper when braking a strong magnet on a pendulum

I recently watched this gif from this video, showing a magnet swinging towards a large disk of copper, where it stops gently before hitting the magnet. I understand that the eddy currents have a ...
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Hysteresis for Niobium superconductor transition

We were having this lab experiment with a Niobium sample: Starting at $5K$ and an applied magnetic field of $20G$ we started heating the sample until superconductivity broke (we basically measured the ...
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Is the streaming of a superliquid through a circular tube equivalent to the current running in a circular piece of superconducting material?

When a superfluid streams endlessly through an isolated circular tube is the same mechanism at work as in the endless current moving through an isolated circular piece of superconducting material? Is ...
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The effect of dielectric bridges on the impedance of a coplanar waveguide

I'll start with some context, but feel free to skip to the third paragraph for the concrete question. I also posted it on the electronics stackexchange, but I think it might have some more chance here ...
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Calculate phonon density of states

I need to calculate phonon density of states for a cuprate superconductor. I know there is a general formula for the calculation of phonon density of states by Einstein models like this $$D(\omega)=(\...
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Kitaev's reason for looking at p-wave superconductors

I would really like to understand the thought process that lead Kitaev to proposing the Kitaev chain but most expositions really just start from the Hamiltonian and derive the Majoranas without any ...
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Perpetual Motion Machine 1: Magnetic Superconductor Loop Generating Energy with Piezoelectrics [closed]

I know there are a lot of perpetual motion machine designs out there, but I haven't found one that looks like this one. I will use this diagram. Assume the entire ring is made of a superconducting "...
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Superconducting order parameter seems to depend on the choice of the ground state wave function!

As it is described in this question the BCS wave function has definite phase but indefinite electron number. Therefore the superconducting order parameter $\langle \phi| c_{k \uparrow}c_{-k \downarrow}...
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Why isn't superconductivity destroyed by the Goldstone modes?

In BCS theory they break particle number conservation and show the existence of a gap, which would explain why groundstate properties stay relatively the same even for higher temperatures (until beta ...
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Cooper Instability in the Fermi surface

When we calculate the Cooper instability with the perturbation theory, we will obtain an effective interaction constant $g^{\prime}=\frac{g}{1-g\nu\ln(\frac{w_D}{T})}$, where $g>0$. The Cooper ...
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Specific heat and latent heat of transformation in superconductors

We know that the specific heat of a superconductor at the transition point (when H=0) is discontinuous. So, the superconductor receives heat without changing temperature. On the other hand, from the ...
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What's the difference between cylindrical geometry and disk with a hole for topological chiral $p_x\!+\!i p_y$ superconductor?

We know that for a topological chiral p-wave superconductor with a cylindrical geometry, i.e. one conserved momentum $k$ and one open boundary direction, there exists edge modes with opposite ...
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Determining the position and spectral weight of Andreev states from a retarded Green Function

I'm trying to understand a result from the paper Josephson current through a correlated quantum level: Andreev states and $\pi$ junction behavior by Vecino, Martin-Rodero and Yetati (2003). ArXiv link ...
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Gauge fixing in Ginzburg-Landau simulation

I am developing a computer simulation of the Ginzburg-Landau model of superconductivity. In a few words, I have discretized the domain with finite differences and I am using Nonlinear Conjugate ...
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Does a superconductor conduct electricity at room temperature?

I know you need to cool a superconductor below a certain temperature for it to exhibit superconductivity, but do superconductors, specifically YBCO superconductors, conduct electricity normally at ...
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What are some examples of magnetocaloric materials?

I've recently become fascinated with a cryo cooling method known as "magnetic refrigeration". Here is the Wikipedia article. I was wondering if there is a list of magnetocaloric materials. ...
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Literature recommendations for superconductivity

What text books / review papers give an easy introduction to superconductivity? The literature should be suitable for Master students with some background knowledge in theoretical solid state physics ...
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Thermalizing bulk superconductors

I have been discussing with some friends whether or not (or how) bulk superconductors thermalize when placed in an environment far below their transition temperature. Suppose you have a cube of pure ...
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What is the atomic limit?

I am attempting to grasp topological superconductivity for an assignment and in trying to understand what makes a quantum system topological have came across the following paragraph; "In the case ...
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Spectral representation of a BCS gap function

I am playing with the spectral representation of a BCS gap function and I have trouble verifying causality properties. I find a divergence and I don't know what is the problem. Assume the gap ...
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spinless and time reversal symmetry breaking of p-wave pairing in topological superconductors

In the context of Majorana zero modes, I often hear that the p-wave pairing is effectively 'spinless' and time reversal symmetry broken. I understand that s-wave and p-wave refer to the spin portion ...
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How does Bohmian Mechanics explain superconductivity?

I'm looking for sources that discuss how Bohmian Mechanics explains superconductivity. Are there still Cooper pairs? Phonons? I saw one vague reference to vortices, but no details. This is my first ...
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What is the difference or connection between inverse proximity effect and triplet proximity effect in superconductors?

I know that inverse proximity effect affect the order parameter of the superconductor and that triplet proximity effect convert singlet Cooper pairs into triplets. But how is the two phenomena ...
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Is it possible to generate Ampere's force between the superconductor and the current-carrying wire?

In superconducting state, There is a current-carrying wire between the superconductor and the magnet,Is it possible to generate Ampere's force between the superconductor and the current-carrying wire?...
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Can superconductors undergo a BKT transition?

In the article by Kosterlitz and Thouless (1973) they write in the abstract: "This type of phase transition (BKT) cannot occur in a superconductor for reasons that are given". Later in the paper they ...
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Why in the BCS ground state the probability amplitudes are taken real?

In some references (see for example Ballentine ch. 18.5) the ground state of the BCS theory is assumed to be \begin{equation} |BCS\rangle = \prod_{\bf k} (u_{\bf k}+v_{\bf k}\hat{c}^{\dagger}_{\bf k,\...
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Reference request on Bogoliubov de Gennes (BdG) formalism

I have tried to gain an understanding about the BdG formalism by just following the calculations I found here and there of people bringing their superconducting Hamiltonians into matrix forms but I am ...
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1answer
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On the magnetic field in the Meissner effect

As shown in the figure, in the Meisner effect, the magnetic field of the magnet bypasses the superconductor. My question is, does the magnetic B field belonging to the magnet increase at the arrow ...
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Energy gap in superconductors and the jump in specific heat

How the energy gap in superconductor arises, and how it is different from the semiconductor band gap? Is it true that jump in specific heat data, assures the energy gap. How to understand it ...
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What is BCS weak coupling Pauli limit?

What is BCS weak coupling Pauli limit Hp? How Hp=1.84Tc relation is derived? Please suggest suitable reference regarding that.
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What is clean limit and dirty limit?

In superconductor there has two limits, one called as clean and other one called dirty limit. But what are that meaning? What means clean and dirty? How the coherence length depends on the electron ...
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Aluminum critical current vs temperature fit

I have some data at different temperatures of Al's critical current (from 600 mK to 1.5K). Tc of Al is ~ 1.3. I am now trying to fit this data to a model to extract the theoretical critical current ...