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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What is the difference between diamagnetism and superconductivity?
Basically, What is the difference diamagnetism and superconductivity?
As far as I understand, diamagnetism comes from the fact, that all electrons in a solid, when exerted by an external magnetic ...
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Normal metal-superconductor action (revealing Andreev reflection)
Short Example
A conventional Josephson junction, which consists of a superconductor-insulator-superconductor (SIS) sandwich and is biased by a constant current $I$, has the following action:
$$S_{SIS}\...
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Interpolation formula for BCS superconducting gap
In BCS theory, the superconducting gap is given by solving at different temperatures the integral
$$\frac{1}{N(0)V}=\int_0^{\hbar\omega_c}\frac{\tanh\frac{1}{2}\beta(\xi^2+\Delta^2)^{1/2}}{(\xi^2+\...
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Kinetic Inductance and Magnetic Flux
Superconductors are known to have kinetic inductance which is the manifestation of the inertial mass of superfluid. In this link, the concept is explained as follows:
When a current flows the ...
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Excitation spectrum in BCS theory and mean field theory
I've recently been learning about the BCS theory of superconductivity. An extremely rough idea is as follows: given the interacting BCS Hamiltonian
$$
H = \sum_{\vec{k}\sigma} \xi_{\vec{k}} c^{\dagger}...
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If BdG Hamiltonian has particle-hole redundancy, how can it be trusted in discussing the topological properties of superconductors?
In BdG Hamiltonians, the particle-hole symmetry is not a true symmetry but rather a redundancy of description. In my oppinion, saying with the presence of particle-hole symmetry is just saying: hey, ...
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BCS state with finite current
How is the BCS state and associated BdG quasiparticle hamiltonian altered by the presence of a finite current? Is there a standard text where this is discussed? (I didn't see anything in Altland and ...
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Spherical symmetry of Cooper pair wave function
Can someone please explain to me how the wave function of a Cooper pair is spherically symmetric?
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Cooper pairs and superconductivity
This might be a dumb series of questions, because I'm not a theoretical or condensed matter physicist.
If there was a method of pairing all electrons before entering a semiconductor, would you ...
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Paramagnetic current density operator in second quantization
I'm reading Tinkham's Superconductivity book and I don't see how Tinkham obtained the following expression for the paramagnetic current density operator (eq. 3.100):
\begin{equation}
J_1=\frac{e \hbar}...
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Kernel in Tinkham's Superconductivity book
I'm reading Tinkham's superconductivity book. I'm having especially trouble with the chapter "electrodynamics". I don't see how Tinham went from the equation below "current density $J_1(...
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Physics of the beaker experiment for superfluid helium
here is an illustration and explanation of the beaker experiment over superfluid helium:
So, according to this experiment, can anyone say what is the cause?
I mean the superfluids are disconnected ...
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’t Hooft 1982 Phys. Scr. 25 133 on superconductivity
In G. ’t Hooft 1982 Phys. Scr. 25 133 paper 'The Topological Mechanism for Permanent Quark Confinement in a Non-Abelian Gauge Theory'
He wrote in the abstract:
We first argue that indeed ...
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Superfluid + Super conductivity in a bose condensate
so my question is this
can we theoretically and empirically find a BOSE condensate, with SUPERFLUID properties but which is also
a SUPERCONDUCTING device ?
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Bogoliubov- de Gennes Hamiltonian and Anti-Commutation Rule
I encounter a problem which is related to Bogoliubov-de Gennes(BdG) Hamiltonian. Suppose I use BdG theory to transform my many body Hamiltonian into the following form:
\begin{equation}
\hat{H} = \...
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How do a superconductor and regular current carrying conductor interact?
Electricity tends to follow the path of least resistance, and superconductors have a resistance of 0. So I was thinking that if a superconductor was connected to GND and brought to a normal current ...
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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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What makes cooper pairs hop to another superconductor?
I know the derivation and how the Josephson effect works. But if we just have two slabs of superconducting material placed together with an insulator between them, what makes the initial hopping occur?...
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Precise Definition of Vortex Halos?
I have read many papers on pair density waves (PDWs) and often time vortex halos are mentioned. These occur when a uniform superconducting component is the dominant order competing with the PDW phase.
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Hamiltonian in second quantization
I'm reading Tinhkam's Superconductivity book and I'm not able to understand how he ended up with Eq. 3.97.
He started with a Hamiltonian $H=\frac{ie\hbar}{m} \sum \limits_i \vec{A} \nabla_i $, used ...
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Why the electric field inside a superconductor is always zero?
Recently I have been reading the book called "Superconductivity, Superfluids and Condensates" from James F. Annett. I was confused by the expression that
zero electric field at all points ...
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How was the superconducting order parameter discovered?
Just wondering if anyone knows the history behind this discovery? The BCS mean field theory suggests a breaking of our $U(1)$ symmetry; hence, a complex order parameter makes sense in that regard. How ...
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Why is there a band structure for strongly correlated systems?
The existence of band structure of a crystalline solid comes from the Bloch theorem, which relies on the independent-electron approximation. Why do people still talk about the band structure for a ...
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Electric currents due to the Coriolis force?
In the Compton generator experiment one uses a hollow glass tube filled with water. When this is flipped over, the water gains a small velocity of the order of 0.1 mm/s for a 1 m radius tube, due to ...
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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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If there's no electric field inside superconductor, then how could there exist current?
If a superconducting wire has infinite conductivity, then there should be zero electric field inside it. However if there's no electric field inside it, there should be no current (as there's no ...
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What would the Capacitance between a Superconductor Plate & a non-Superconductor Plate?
Assume Plate 1 is Superconducting, and completely isolated(no attached non-superconducting conductor connection) but has a small (nA or $\mu$A) continuous current
Assume Plate 1 is separated from ...
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Why do doped Mott Insulators describe high Tc Superconductors
Often people justify research on Mott Insulators / Hubbard model because a "doped" (added impurities) Mott Insulator may be useful in describing high Tc-superconductors like the cuprates.
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How does q superconductor moves along a line of magnets if it's flux-pinned?
So I saw a plenty of demonstrations where superconducting piece of material moves freely along a magnetic surface, usually a line of arranged magnets, and at the same time it is claimed that flux ...
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Particle-hole statistics relation with superconductors
I have a problem regarding the Fermi-Dirac (FD) functions and the relation between particles and hole.
The FD distribution for an electron is
$$ f^e(\varepsilon) = \frac{1}{1+\exp(\frac{\varepsilon-\...
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What would be the maximum critical magnetic field of superconducting hydrogen?
Say you have a superconductor made of metallic hydrogen. What would the be the maximum critical magnetic field?
I know that the new superconducting magnets such as YBCO can reach field strengths of up ...
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Is there spin-singlet $p$-wave superconductivity?
Superconductor-proximitized materials with spin-orbit coupling are expected to host $p$-wave superconductivity.
In Alicea2010, it seems like that the superconducting proximity induced effective p-wave ...
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Do the accelerated (-2 charged) Cooper pairs in a closed superconducting circuit emit photons?
According to my current knowledge, the Cooper-pairs in a closed superconducting circuit should "feel" a centrifugal force. The (-2) charged pairs are therefore accelerated.
Do the Cooper ...
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Does the theory of holographic superconductors have any application?
I recently became aware of the relatively novel concept of holographic superconductors, and I was wondering whether anyone here has read something about experimental application of these theories.
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Density states of Cooper pairs
In superconductivity we can treat the electrons of a Cooper pair as a boson and electrons can occupy the same energy level. But for temperatures above $0$ K and below $T_c$ not all electrons will be ...
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Resistance of superconductors [duplicate]
Is the resistance of superconductor,in reality, actually zero? Or is it too low (negligible resistance)?
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BCS and Feynman Diagrams
I am currently studying the strong coupling theory (by Eliashberg) of superconductivity, which is derived by BCS by considering self-energy diagrams and the following interaction potential
$$ V(q, i\...
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Is Meissner effect really caused by expulsion of magnetic flux?
The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state.
This is the explanation by mainstream physics.
But the experiments ...
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How does too much current 'kill' a type-2 superconductor?
I recently saw this post: Can a superconducting wire conduct unlimited current?
One of the responses mentioned the Meissner effect. However, I am aware that this occurs primarily in type-1 ...
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Thermal conductivity of superconducting material
I design a thermal management system. I came across the idea that superconducting material (at the proper temperature) can be used as a perfect heat conductor.
My question is
"Do superconducting ...
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Can (anti)ferromagnet be superconductor by proximity effect?
If I put a very thin (anti)ferromagnet between two superconductors, is it possible to become a superconductor via proximity effect? For example, a supercurrent exists with zero voltage drop.
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Group Theory of Superconducting Order Parameters?
In crystalline superconductors, the order parameter $\Delta(\mathbf{k})$ (aka gap, or Cooper pair wavefunction) can be classified by its symmetry according to the representations of the symmetry group ...
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How to fit Werthamer-Helfand-Hohenberg (WHH) equation in a $H_{c2}$ vs $T$ equation?
The Werthamer-Helfand-Hohenberg (WHH) formula $$μ_0H_{c2}(0)=0.693μ_0T_c\frac{dH_{c2}}{dT}|T→Tc$$
was used to estimate μ$_0$H$_c$2(0) at 0 K where only orbital breaking effects are considered in the ...
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How is the BCS ground state a coherent state?
A coherent state is defined as the eigenstate of the annihilation operator $\hat{a}$. It can be obtained from the vacuum of the number operator by acting with displacement operator: $$|z\rangle=\hat{D}...
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Inductance in Superconductors
This is a picture I got from a question in this website, it seems totally fine, but if you try looking it gain, is the heater placed in the wrong position? Because as I know current takes the path of ...
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Ginzburg-Landau and Coherence Length
Consider the Ginzburg-Landau functional for a complex function $\psi:\mathbb{R}^3 \to \mathbb{C}$, i.e.,
$$
F[\psi]=\int \frac{1}{2M}|(-i\hbar\nabla -eA)\psi|^2+r|\psi|^2+\frac{u}{2}|\psi|^4 + \frac{B^...
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BCS theory energy gap
I am studying BCS theory of superconductivity and have understood everything except this part: According to HyperPhysics "The electron pairs have a slightly lower energy and leave an energy gap ...
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Resistance in superconductor with quasi-particle
If current is applied to a superconductor with quasi-particles, that is an excited superconductor,
will the voltage be measured within the superconductor?
In my opinion, when the current is applied, ...
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What is a 'multi-energy band' superconductor?
From Phys.org:
They write that in lab experiments they've found a short-lived "Higgs mode" within iron-based, high-temperature (but still very cold), multi-energy band, unconventional ...
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Holographic and BCS Superconductors
The AdS/CFT correspondence can explain superconductors in a holographic way, using bulk gravity with a black hole in the background and a scalar field which, under suitable conditions, acquires a VEV ...
