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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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What effect would a positron source have on a superconductor's electron flow?

Let's say you have current flowing through a superconductor placed close to a steady source of positrons. What effect would the positrons have on the current? Would the positrons annihilate some of ...
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How can the Objective Reduction theory of quantum mechanics account for macroscopic quantum systems?

In Penrose's OR (Objective Reduction) theory, the time taken for the wave function to collapse is τ ≈ ℏ / E_G (https://en.wikipedia.org/wiki/...
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How does phase gets aligned in a superconductor?

I am trying to make an analogy between the spontaneous symmetry breaking occurring in magnetism and that of superconducvity, but I am struggling to make it precise. In magnetism, we know that ...
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Josephson energy versus magnetic field in S-Nanowire-S junctions

I was reading the proposal Microwave transitions as a signature of coherent parity mixing effects in the Majorana-transmon qubit by Ginossar and Grosfeld (2014) in which they envision a superconductor-...
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Quasiclassical propagator

Sometimes they are referred as Keldysh quasiclassical propagator or Eilenberger propagator. How the quasiclassical propagator is derived? How they are implement with a simple case of a Green's ...
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What is the precise/defining mathematical behaviour for Meissner effect?

This video derives the Meissner effect $$\textbf{B}(x)=\textbf{B}(0)e^{-x/\lambda},$$ by reducing the equation, $$(\nabla^2-\lambda^{-2})\textbf{B}(\textbf{r})=0\tag{1}$$ into its one-dimensional ...
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What are disordered superconductors? What kind of research is done in this area?

I was talking with a friend of mine and he mentioned that his professor does research on disordered superconductivity. I had a rough idea of what superconductivity is, but when I looked up the term "...
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quark momentum and quark mass in unpairing and pairing phase

In this Review paper in p.1464, top left: Rev.Mod.Phys.80:1455-1515,2008 -- Color superconductivity in dense quark matter It shows a figure of quark momentum of quark $u,d,s$, in unpairing and ...
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Quark pair superconductor: Even parity is favorred than odd parity

It seems that the quark pair superconductor can be odd or even parity pairing respect to the parity $P$. Say that the even parity has the form: $$ \langle\psi C \gamma^5 \psi\rangle $$ the odd ...
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Superconducting wire with temperature gradient

If you have a piece of wire that is a superconductor (say Niobium), and you hold the temperature at one end above $T_c$, and the other end below $T_c$ -- would you have a state of both superconducting ...
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Penetration depths in a type II superconductor

Let's consider a type II superconductor as a dissipative medium, so that it possesses a penetration depth (also called skin depth) that can act upon a penetrating time-varying EM field (affecting both ...
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What is superconducting coherence length?

I'm an electronics student, and don't know much about some physics concepts. I was studying superconductivity and came to the London equation, Meissner effect and BCS theory. I kind of understood ...
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Estimate of correlation length for Cooper pair

I am following the derivation of the radial wavefunction and correlation length of a Cooper pair in Walter Greiner's book "Quantum Mechanics - Special Chapters". While I understand how to obtain the ...
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Original derivation of the Josephson effect

In my efforts to understand Josephson's original derivation of the effect that bears his name, I was led to Eqs. 3.68 on pg. 69 from Tinkham's book (Introduction to Superconductivity, McGraw-Hill, 2nd ...
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What type of superconductors does Maglev train use and why? [closed]

I would like to find out what type of superconductors does the Maglev train use and why is this is this specific type? As I cannot find it anywhere on the net. Thank you!
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To pi or not to pi?

Some research articles normalize superconductor Green's function to satisfy this condition $G^2=1$. Others use different condition $G^2=-\pi^2$. Why there is a difference? What is the purpose of ...
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Relationship between the validity of mean field treatment and the strength of coupling/interaction

Mean field is a quite common treatment in studying phase transition and critical phenomena, although it neglects fluctuations. Imagine we have a Hamiltonian consists of free part and interaction part:...
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There is no electric field in a metal if the current through the conductor remains constant.

In a chapter of superconductor, I found, "There is no electric field in a metal if the current through the conductor remains constant". My question is, "Why the electric field is zero in such case?". ...
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Spatially uniform VEV for gauged Ginzburg-Landau functional

The Ginzburg-Landau functional reads: $$F = \int dV \left \{\alpha |\psi|^2 + \frac{\beta}{2}|\psi|^4 + \frac{1}{2m^*} \mid (\frac{\hbar}{i}\nabla - \frac{e^*}{c}A)\psi \mid^2 + \frac{h^2}{8\pi}\...
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Can cooper pair formation take place between electrons having same spin?

Since they're bosons, can cooper pairs have spin values other than zero like 1? If the electrons had the same spin, can't their spins add up as 1/2+ 1/2?. Thanks in advance.
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Do defective filaments still conduct in multi-filament superconductor wire ?

In a super conducting multi-filament wire, if a particular filament within the wire has a break for instance from a nanometer size occlusion, will induction partially or completely make up for the ...
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277 views

Capacitor in a superconducting circuit

Assume we have started a current in a closed circuit which only includes a capacitor. No inductor. For example by having a battery initially, disconnecting and and reclosing the circuit. For a ...
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Why there is no Knight shift for a spin-triplet p-wave superconductor?

In the Nature article: Spin-triplet superconductivity in $Sr_2RuO_4$ identified by ${^{17}}$O Knight shift https://www.nature.com/articles/25315 Authors state: For a spin-triplet p-wave ...
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How would a truly zero ohm loop of wire behave in space?

This is a purely hypothetical question as 0 resistance is impossible to create. That being said, I was thinking about this and came to a conclusion that I couldn't understand, so I assumed I must have ...
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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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BCS quadratic Hamiltonian: confused with operators

I'm working through J. Annet book: Superconductivity, Superfluids and Condensates. In chapter 6 (BCS theory) the effective Hamiltonian in quadratic form is introduced: $$\sum_{k\sigma} (\epsilon_k - ...
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Basic doubt superconducting qubits

This is a basic doubt regarding the principle behind superconducting qubits: What I understand is when we add a Josephson junction to a standard LC circuit, it adds anharmonic behaviour, but what I ...
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If I have electric current going through a superconductor and cut off the power in what fraction of a second will the electrons stop moving?

If I have electric current going through a superconductor and instantly cut off the power supply(rendering the circuit open, and not at all closed), In what tiny fraction of a second will the flowing ...
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How a non-zero superconducting order parameter translates to superconducting bebaviour?

In this question, I asked how the link can be made between the property of superconductivity and the BCS ground state. I would now like to extend this question to a general state. That is, if I have ...
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Unfamiliar with some notations of BdG Hamiltonian

In a paper Majorana Fermions in Equilibrium and in Driven Cold-Atom Quantum Wires. The authors come to a Hamiltonian for BdG, eqn(2). $$ H = \sum_{p} a_{p}^{\dagger}(\epsilon'_{p}-\mu+u p \sigma_{z}+B\...
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A microscopic derivation of the Josephson effect

It is a little bit surprising to me that it seems hard to find a detailed, microscopic derivation of the Josephson effect. Generally, you see a hand-waving derivation based on the macroscopic ...
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Is electricity perpetual in a superconductor system?

I wonder if electricity consumption happen according to the Law of conservation of energy and Joule effect, in a regular circuit certain amount of energy is transformed into heat by components ...
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Introductory condensed matter physics book [duplicate]

I need a book for general condensed matter physics, preferably at an undergraduate level, e.g. at Ashcroft and Mermin's level or below. Modern applications are preferred.
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Superconductivity and superfluidity in bosonic and fermionic condensates

Can bosonic and fermionic condensates explain superfluid and superconducting properties? Are they better than the theory of BCS and Landau? Edited: My question is based in this lecture pesentation ...
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Free energy term for the magnetic field in Ginzburg-Landau theory

The present question is related to this physics.SE post. In Ginzburg-Landau theory, the free energy of the superconductor can be written as $$F = F_n + \alpha |\psi|^2 + \frac{\beta}{2} |\psi|^4 + \...
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Ginzburg-Landau integral

My question is exactly the same as this question, but I cannot do the variation of integral referred in the Addendum, i.e., \begin{align} S_B\propto\int dx\; B^2=\int \left(\nabla\times A\right)^2\; ...
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Does the proximity effect in semiconductor/superconductor heterostructures require an accumulation layer

I've recently been looking at literature on the proximity effect in semiconductor-superconductor heterostructures, where the semiconductor takes on superconductivity over mesoscopic distances. ...
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Regard to the technical definition of a Mott insulator

I was reading Chapter 16 of the textbook on advanced solid state physics by Philip Phillips. In this chapter, the physics of Mottness is comprehensively discussed. There is a statement he made on page ...
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Magnetic Field dependence of the Hall coefficient in cuprate

The magnetic $H$-Field dependence of the Hall coefficient in cuprate YBCO are shown in a, b. Hall coefficient ($R_H$) of YBCO at various fixed temperatures, as indicated, plotted as $R_H$ versus $H/...
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How to conceptually think of Cooper pairs in a superconductor

I'm trying to improve my conceptual understanding of Cooper pairs in a superconductor. Not how they come about such as discussed in this question, but more in the sense of what kind of picture I ...
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1answer
154 views

Electromagnetic waves through perfect diamagnetic (superconductor)

Electromagnetic waves move through the space by varying electric and magnetic fields in the space. My question is that how can they cross a material through which which there is no magnetic field. I ...
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How to derive energy dependent Gamma and Delta of topological nanowire?

I read two articles, G. Tkachov, and E. M. Hankiewicz. “Spin-helical transport in normal and superconducting topological insulators.” physica status solidi (b) 250, no. 2 (2013): 215. (arXiv) ...
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Instanton effects on condensates: (pseudo)scalars, (pseudo)vectors, tensor

I have heard that the instanton effect in quark matter causes the di-quark condensate to be Lorentz scalar. As opposed to the Lorentz scalar, there are possibilities that the condensates are Lorentz ...
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Volovik's argument and superconductivity

In Volovik's book he describes the Fermi surface as a vortex in energy+momentum space. Due to a winding number the Fermi surface is topologically protected. I don't understand how the above ...
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How to visualize multi-dimensions in topological periodic table?

This is a question for those who are familiar with topological periodic table. The first row and right side columns represents dimensions of topological materials in periodic table. I know that for ...
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Infinite-fermion condensed $\langle \psi^n \rangle$ superconductor as $U(1)_f$ QED

I find it puzzling to consider the relation between (1) and (2). (1) The superconductor obtained from an infinite number of fermion condensation $\langle \psi^n \rangle$ with a $n \to \infty$ with a ...
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Flux quantization in a superconductor and Berry phase

In the derivation of flux quantization for a superconducting ring, we say that $$\oint_C \nabla\theta . dl = \theta_{2} - \theta_{1}$$ Then we equate this value to $2\pi n$. The reason cited in ...
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Difference Between Adiabatic and Superconducting Quantum Computing

Wikipedia (not the most stringent source, I know) has separate pages for adiabatic and superconducting quantum computing. It's my understanding that all superconducting quantum computers are adiabatic ...
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London equations - what is the mass is present?

The London equations are given by: \[ \newcommand{\p}[2]{\frac{\partial #1}{\partial #2}} \newcommand{\f}[2]{\frac{ #1}{ #2}} \newcommand{\l}[0]{\left(} \newcommand{\r}[0]{\right)} \newcommand{\mean}[...
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Terminology surrounding superconductors and the Meissner-Ochsenfeld effect

As stated in (Annett, 2004;pg 55) not all materials whose resistances vanishes exhibit the Meissner-Ochsenfeld effect (MOE). Which of these is therefore the defining property of a superconductor (if ...