Superconductivity is the transmission of current with no resistive losses, and is one of the most active areas of condensed matter physics research.

learn more… | top users | synonyms (1)

0
votes
0answers
10 views

Switching Parity in a Superconductor

I've got a pretty simple question that's been bothering me for a while. This is the issue. Suppose we have a superconductor with phase $\phi$, and we change this to $\phi+2\pi$. One would think that ...
10
votes
1answer
294 views

Are there topological non-trivial states in zero dimension?

The periodic table of topological insulators and superconductors suggests that there can be topological non-trivial phases in zero dimension in non-interacting system with certain symmetries. A 0D ...
2
votes
1answer
46 views

Gauge Theory of Superconductors

I'm trying to understand better the nature of the gauge redundancy and the Higgs mechanism in superconductors. Specifically, I'm looking for a good reference that explains monopoles, vortices, and ...
0
votes
0answers
18 views

Charge balance and Bogoliubov quasiparticles

Before trying to understand charge imbalance in superconductors (eg Hübler et al., Phys. Rev. B 81, 184524, Quay et al., Nature Physics 9,84–88 (2013)) I thought I had better check I understand the ...
0
votes
1answer
126 views

Superconductor in a parallel vs perpendicular magnetic field

My question concern's the huge difference in critical fields regarding a thin superconductor(SC) which is surrounded by a magnetic field. lets imagine the SC is a thin film in the x-y Plane: Applying ...
5
votes
0answers
62 views

What happens to a radar signal when it meets with a superconductor? [duplicate]

A radar system has a transmitter that emits radio waves called a radar signal, consisting of electromagnetic radiation. What happens when it meets with a strong superconductor, considering the fact ...
0
votes
0answers
18 views

Can neutrons detect the diamagnetic effects of superconductivity?

It is well known that an applied magnetic field to a superconducting material produces a diamagnetic response due to the induced screening currents. Neutrons used as a probe for magnetism and crystal ...
2
votes
1answer
302 views

What kinds of behavioural anomalies can a zero-field-cooled (ZFC) / field-cooled (FC) split indicate?

If a material shows a spiltting in the ZFC and FC curves, is it necessarily superparamagnetic, or could there be any other reason for the irreversibility? I have heard spin glasses also show ZFC-FC ...
1
vote
1answer
145 views

Do magnets also attract super conductors?

If a superconductor can be repelled by a magnet (or, well, locked in a certain position by the magnet) can a magnet be attracted to a superconductor. What would happen if you take a peace of metal, ...
5
votes
1answer
68 views

Electric charge conservation in a superconductor

In a superconductor, $U(1)$ gauge symmetry is spontaneously broken. But $U(1)$ gauge symmetry is responsible for conservation of electric charge. Then it appears to me that the electric charge ...
1
vote
2answers
63 views

Could superconducting magnets be used to form a shield around a spacecraft?

If superconducting magnets could be used in space to form a field around a spacecraft of a similar field strength on the earth 25 to 65 microtesla's? Would the temperature in space at -246c be OK ...
0
votes
1answer
45 views

Is it true that in a superconductor the current will always flow without a any electric source? [closed]

It came to my mind that when a superconductor is taken and a wire is joined to it to make it a complete circuit, the current is flowing through it. Now, I am removing the battery and joining the two ...
4
votes
1answer
42 views

Something about non BCS pairing

When I have read about literatures, the non-BCS type superconductor always involve some kind of pairing which the energy gap $\Delta$ is not a constant but a function of momentum $k$: $\Delta=\Delta(k)...
0
votes
0answers
26 views

Distinguishing Insulator, Metal, Superconductor by a flux insertion argument

I have the following argument to distinguish Insulator, Metal and Superconductor. For simplicity let's consider electrons on a circle and thread one quantum of flux (e$\Phi_0 = 2\pi$) through it (or ...
1
vote
4answers
49 views

what's the difference of the gap between superconductor and insulator

This is what I learned from textbook. An insulator is insulate as the gap between the valence band and the conduction band and the fermi level lies in the gap. A superconductor is super electronically ...
12
votes
1answer
218 views

Monopoles and the magnetic Higgs mechanism

In a paper of 't Hooft about the rôle of magnetic monopoles for a model of quark confinement, I don't understand the following sentence (end at paragraph 14) [...] in order for monopoles to ...
5
votes
1answer
266 views

Superconductivity in graphene with spin orbital coupling, is it proper to let the order parameter on two sub-lattice equal?

I am reading this article: Edge superconducting correlation in the attractive-U Kane-Mele-Hubbard model. Considering just the first part of the article, where a negative-U Hubbard model with the ...
5
votes
1answer
157 views

How is superconducting coherence length measured in experiment?

In a superconductor, the coherence length measure the mean distance between two electrons in the Cooper pair. How is the coherence length experimentally measured?
5
votes
1answer
314 views

What is a d + id superconductor and why does it break time reversal symmetry?

There are a lot of publications dealing with d-wave and d + id superconductivity, but I found no satisfying answer what exactly makes a superconductor d + id and why they break time reversal symmetry. ...
10
votes
1answer
197 views

Is the uniqueness theorem correct in superconductivity?

There is an uniqueness theorem in electromagnetism. It says that the solution of Maxwell's Equations is determined uniquely by boundary conditions. We can treat superconductivity as a completely ...
4
votes
1answer
511 views

Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
3
votes
2answers
185 views

Charging by induction

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
2
votes
1answer
43 views

Is edge states of topological insulators superconducting?

I am told edge states of topological insulators are free from back scattering. Does this mean topological insulators have no resistance if only edge states are taken into account?
0
votes
0answers
8 views

What kind of flux-pinning effect will occur if a type two superconductor is subjected to an AC electromagnet?

When a supercooled type two superconductor is subjected to a static magnetic field, the superconductor pins to the flux of the field (the mixed-state meissner effect is apparent). What happens if it ...
1
vote
2answers
107 views

Concepts regarding BCS Theory of superconductivity and Cooper pairs

I have a little conceptual doubt about the BCS theory of superconductivity. A visual model of the Cooper pair attraction has a passing electron which attracts the lattice, causing a slight ripple ...
0
votes
0answers
33 views

How to understand Superconductivity in a particle number fixed system at zero temperature?

The BCS wave function doesn't have fixed particle number. And this is called U(1) symmetry breaking by many people. But if we are given a system with fixed particle number, how can we understand ...
20
votes
1answer
301 views

Should a superconductor act as a perfect mirror?

I have been told that metals are good reflectors because they are good conductors. Since Electric fields in conductors cause the electrons to move until they cancel out the field, there really can't ...
2
votes
0answers
2k views

How to understand the equivalence between Andreev reflection and Cooper pair injection?

It is well know that Andreev reflection dominates the subgap transport at the normal metal-superconductor interface. An incident electron can be reflected as a hole in the Nambu space, which ...
6
votes
2answers
184 views

How do we explain the existence of liquids, from a mathematical or computational perspective? [closed]

This post asks why matter exists in three phases. Most of its answers explain the existence of liquids with some variant of the following: liquids happen when thermodynamic conditions, temperature ...
8
votes
3answers
126 views

Validity of mean-field approximation

In mean-field approximation we replace the interaction term of the Hamiltonian by a term, which is quadratic in creation and annihilation operators. For example, in the case of the BCS theory, where $...
1
vote
0answers
28 views

Four point probe method under liquid nitrogen

I was trying to measure the resistivity of the YBCO superconductor (but not like a resistivity- T diagram, but only at liquid nitrogen boiling point), so I needed to put the sample in thermal contact ...
1
vote
1answer
52 views

Eddy currents in a superconductor

Just had a lesson we just had our teacher introduced the concept of eddy currents, and showed us how a magnet moves slowly through a metal tube due to the opposite generated magnetic field. If you ...
13
votes
1answer
178 views

Synthesis of Fe-based superconductors

Polycrystal cuprate superconductors are generally prepared by solid state reactions: Starting reagents are in powder form, they are mixed to each other and placed into furnace on high temperature (...
3
votes
1answer
57 views
1
vote
1answer
77 views

Cooper pairing from repulsive potential

Suppose the Hamiltonian of a many-electron system consists of a potential which is repulsive : $\langle k_1, k_2 |\hat V |k_1',k_2' \rangle > 0$ where $k_1, k_2, \cdots$ are possible momenta that ...
1
vote
0answers
26 views

Magnetic moment of superconductors

How would a superconductor's magnetic moment be affected when it is placed in an increasing magnetic field? I know that as the magnetic field gets stronger, fluxons begin to penetrate into the ...
4
votes
3answers
4k views

Quantum levitation (locking) 3mm thick disk could carry 1000kg small car claim

I watched this TED presentation: http://www.ted.com/talks/boaz_almog_levitates_a_superconductor.html It is about superconductivity and quantum levitation. It tells that super-thin, three-inch disk ...
5
votes
1answer
49 views

Super conductivity and energy gap in fermionic/bosonic subspaces

I am trying to understand the phenomena of super-conductivity from a broader level. What I understand for now is that for super-conductivity to be possible in a system, a necessary requirement is that ...
1
vote
0answers
75 views

Bogoliubov transformation with two pairing terms

Let us assume that we have a Hamiltonian of the form: $$ H = \sum_{k,\sigma,s}\epsilon_{\sigma s}\left(k\right)c_{k\sigma s}^{\dagger}c_{k\sigma s} + \sum_{k,s}\Delta_{0}\left(k\right)c_{k\uparrow s}^...
0
votes
0answers
13 views

How much damping is there being exerted on a vertically stable magnet moving across a superconductor surface?

I'm thinking of a flat magnet with opposite poles on the wide ends, though perhaps some other arrangement is more stable. Assuming such a magnet is levitating in a completely stable state and is ...
1
vote
0answers
34 views

Magnetic field interaction energy term

I am trying to derive the Ginzburg-Landau free energy for superconductors, and I follow most of it apart from the introduction on the term containing the magnetic field. This is the bit I don't ...
0
votes
1answer
28 views

Why is superconductance not observed at regular ambient temperatures?

I have done some reading on superconductance and understand that the reason it happens is due to the formation of Cooper pairs resulting from the attractive momentary charge concentration resulting ...
0
votes
1answer
26 views

can superconductors and other meisner materials be used as magnetic shielding in space to protect diamagnetic artificial gravity of 45 teslas?

I have seen people referring to Geim's floating frog that a human in 45 Tesla's would be held to the ground from diamagnetism above them. A very real but crude artificial gravity using powerful ...
5
votes
2answers
67 views

What do we know about the strength of the electron-phonon coupling in high-temperature superconductors?

I would like to clarify the situation of the electron-phonon coupling in high-temperature superconductors (or considering only the cuprates). The main question is what do we know about the strength of ...
2
votes
1answer
47 views

Why is the symmetric phase in a Bose gas not superfluid?

In the theory of superfluidity in weakly interacting Bose gases, one finds that in the symmetric phase the exctitations have the dispersion relation $\omega = \frac{k^2}{2m}-\mu$ with gap $\Delta=-\...
4
votes
1answer
465 views

Majorana bound states in the Bogoliubov-de Gennes (BdG) formalism

I have the Kitaev chain tight-binding Hamiltonian into the BdG formalism (like the one in the "Bulk-edge correspondence in the Kitaev chain" section of Week 1 of this course http://www.topocondmat.org/...
2
votes
1answer
68 views

Boundaries in superconductors

In quantum mechanics we have the famous example of a particle in a box. The finite size of the System leads to a quantization of the momentum of the particle due to the Formation of standing waves in ...
4
votes
2answers
104 views

How to write BdG Hamiltonian in graphene?

In Beenakker's paper:Specular Andreev Reflection in Graphene, the BdG Hamiltonian is written as: $$ H_{BdG}=\begin{pmatrix}H-E_F&\Delta\\ \Delta^*& E_F-H\end{pmatrix} $$ from equation (1). ...
0
votes
0answers
44 views

Equation for Electric and Magnetic field from the equation for a “massive photon”

I was reading the Quantum Field Theory book by Maggiore. There he says that in side a superconductor the photon satisfies the equation $$(\Box+m^2)A_\mu=0$$ Then he adds that the electric field and ...
1
vote
0answers
80 views

Nambu notation and the Majorana bound state

In celebrated work of Fu and Kane they show appearance of Majorana bound state thanks to presence of superconductor and surface states of topological insulator. They write Hamiltonian $H = \tfrac{1}{...