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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Superconductivity as a macroscopic phenomena

I have been doing some reading on the formulation of BCS superconductivity. From what I understand, an additional non-vanishing term $\Delta c_{\uparrow,k}c_{\downarrow,-k} + c.c$ develops below the ...
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Particle Hole symmetry in Interacting superconductor

For noninteracting superconductors (fermion hopping plus fermion pairing), there is a particle hole (PH) symmetry which is a redundancy. The redundancy says that the BdG Hamiltonian satisfies the ...
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Why do magnetic field lines wrap around the other side of a super diamagnet instead of redirecting completely away?

Super conductors are perfectly diamagnetic in that they perfectly expel a magnetic field. To me that means that if the source of a magnetic field is on one side of a super conductor, the other side ...
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Diamagnetic current in the BdG superconductor

Recently, I am following the paper arXiv:1610.01803 to study superfluid weight. In this paper the diamagnetic current is given by: $j^D_{\mu}(\vec{q})=\sum_{\vec{k},\sigma}\partial_{\mu}\partial_{\...
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Laminar structure

I am currently reading 'Introduction to Superconductivity' by Michael Tinkham. In the second chapter (introduction to electrodynamics of superconductors) Tinkham goes on to describe the idea of the ...
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BCS theory and Cooper pairs

I'm studying superconductivity and BCS theory. Looking at the BCS ground state construction, I see two things that seem conflicting Occupation of Cooper pairs in BCS ground state (look at the figure ...
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Would we need a battery if there was no resistance?

I'm struggling to wrap my head around this idea. Imagine that we have a wire with no resistance ($R=0$). According to Ohm's law $V=IR$, the voltage drop ($V$) between any two points would be 0, and ...
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Dimagnetism proof for superconductivity

I came across an article that dimagnetism is one of the proof so that a material can act as superconductor. So what is dimagnetism.
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What is the effect of the global $U(1)$ spontaneous symmetry breaking on the physical observables in superconductors?

I have been taught that in Ginzburg-Landau model for superconductors the transition to the superconductive states lead to the spontaneous symmetry breaking of global $U(1)$ symmetry. While I have ...
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Is there a theoretical ground for ionic superconductivity?

I've been wondering for a while if there's a possible theoretical ground for ionic superconductivity, or whether it is at all possible from a thermodynamic and condensed matter physics standpoint. ...
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Wavefunction of Cooper Pairs

I tried to solve the wave-function of cooper pairs but i am stuck in an integral equation and have no idea how to solve for the wave-function. Before, i tell you how i got the integral in brief. ...
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Is Meissner effect really caused by expulsion of magnetic flux?

The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state. This is the explanation by mainstream physics. But the experiments ...
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Can you lock multiple magnets to a single superconducting puck?

We've all seen the videos of a superconducting puck floating above a track of magnets. Could another magnet be locked above the puck? I ask this with the intention of attaching vacuum insulator to the ...
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flux threading through superconducting ring

I have been confused over the wording used in this paper describing RSFQ logic circuits: http://www.mukhanov.com/uploads/LikharevSemenov-RSFQReview_IEEETAS91.pdf From page 6: " If such a single flux ...
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Position of coherence peaks in linear density of states for d-wave and extended s-wave symmetry

Where do the coherence peak singularities in the linear density of states lie for d-wave and extended s-wave pairing symmetries? In particular, what is the value of the gap between the coherence peaks ...
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Eigenvectors of the BCS Hamiltonian

In introductory superconductivity one often studies the BCS Hamiltonian $$H= \begin{pmatrix} \xi & -\Delta \\ -\Delta & -\xi \end{pmatrix} $$ I can find the Eigenvalues and Eigenvectors by ...
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Spin rotation symmetry in triplet superconductors

Triplet superconductors can be described using the $d$ vector formalism and many properties of the superconducting states can be checked via operations on the $d$ vector itself. I want to know how can ...
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Why is mercury a type I superconductor and Niobium is a type II superconductor? What makes them two different types of superconductor?

What structural and physical differences are there that separates Nb and Pb into two different type of superconductor?
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How does Cooper pair move in a lattice according to BCS

According to BCS theory, the cooper pairs have opposite momenta, but according to this animation http://www.superconductors.org/bcs_anim.GIF the electrons in the pair seem to move in the same ...
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Characteristic lengths in SNS Josephson Junction

An S-N-S Josephson junction is formed by two Superconducting (S) leads separated by a normal metal (N) which acts like the weak link. While studying, I often encounter the words diffusive, long, ...
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Topological superconductors

I have been reading a lot about quantum computation by using topological materials and I could see that the standard approach is to engineer a p-wave superconductor by using a 1-D semiconductor wire ...
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How to plot Majorana energies for Kitaev chain as function of mu?

My first attempt was, using the Python library Kwant, getting the lowest eigenvalues for the 1D p-wave superconductor as a function of the chemical potential mu (In the image below I show what I got). ...
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Hamiltonian in Piers Coleman - Introduction to Many-Body Physics book

In the book "Piers Coleman - Introduction to Many-Body Physics (2016, Cambridge University Press)" in page 491 When an electron pair is created, electrons can only be added above the Fermi ...
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Superconductivity at room temperature [duplicate]

Why superconductivity at room temperature is SO important that the physics world is running behind it like AI in computer science field?
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Nature of density of states for d-wave, s-wave and extended s-wave pairing symmetries

For d-wave, $\Delta(k)=\Delta_{d} (\cos{(k_{x})}-\cos{(k_{y})})$ For s-wave, $\Delta(k)=\Delta_{0}$ For extended s-wave ,$\Delta(k)=\Delta_{s} (\cos{(k_{x})}+\cos{(k_{y})})$ How will be the nature ...
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How to fit Werthamer-Helfand-Hohenberg (WHH) equation in a Hc2 vs T equation?

The Werthamer-Helfand-Hohenberg (WHH) formula $$μ_0H_{c2}(0)=0.693μ_0T_c\frac{dH_{c2}}{dT}|T→Tc$$ was used to estimate μ$_0$H$_c$2(0) at 0 K where only orbital breaking effects are considered in the ...
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Magnetic field on a super conductor cylinder

Suppose that i have a cylinder of the z axis. I'll put this cylinder on a uniform magnetic field with magnitude of B0 along de y axis. Since we have B = 0 inside the superconductor, this will ...
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Interface boundary conditions of superconductor

Are the usual interface conditions for electromagnetic fields, i.e. $$\mathbf{n}_{12}\times(\mathbf{E}_1-\mathbf{E}_2) = 0,$$ $$\mathbf{n}_{12}\bullet(\mathbf{D}_1-\mathbf{D}_2) = \sigma_s,$$ $$\...
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Creating a spatial variation of phase in a given superconducting sample

Blundell's book on Magnetism, talks about the generalized rigidities as a general consequence of spontaneously broken symmetries. In this context, it mentions that in a superconductor the phase of the ...
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How to extract energy band gap of a superconductor by fitting s wave model in electronic specific heat data?

The image is self explanatory.However, I want to know, how can i fit $C_el$ using equn. 16 which is dependent on 15. Please help with steps. Do i have to perform numerical integration?
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Anderson-Higgs Mechanism

Consider an abelian gauge field coupled with a complex field: $$\mathcal{L}=-\frac{1}{4}F_{\mu\nu}F^{\mu\nu}+(D\varphi)^\dagger D\varphi+\mu^2 \varphi^\dagger\varphi-\lambda(\varphi^\dagger\varphi)^2.$...
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The Energy Spectrum of Bound states in the Vortex Core of Type II Superconductors

In the calculation of the so-called Caroli-de Gennes energy states in a type II superconductor the following Bogoliubov-de Gennes Hamiltonian is used: $$ H=- (\frac{1}{2m}(\nabla+ie\mathbf{A}\sigma_z)^...
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What is the reason why at low temperatures the electromagnetic interaction becomes short ranged?

We know that at very low temperatures, the electrons start forming Cooper pairs and generate some sort of eddy current, so that a magnetic flux that is trying to penetrate the low-temperature object ...
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Can electrons fly off a conductor?

This is probably a stupid question, but what if you made an electron flow through a superconductor so that the electrons build up speed flowing through the wire, and then cut the wire. Would the ...
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What is the significance of noise which appeared in the experiments conducted by IISC students on superconductivity at room temperature? [closed]

A pair of Indian scientists may have just discovered the first superconductor material that works at room temperature. Their finding – which is currently surrounded by controversy – comes ten months ...
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Turning into superconductivity---continuous or discontinuous?

The figure below is Onnes' original data. The transition region is very narrow. It suggests a first order phase transition, but still not so conclusive. What is the latest understanding of the ...
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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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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] \...