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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Destroying currents in superconducting rings by vortex tunneling

Consider a superconducting metal ring in which there is a persisting current $I$. I am interested in the failure of this current to remain "persisting" in the ring, although this will occur at ...
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About recent experimental evidence of Majorana edge states in topological superconductors

I have a couple of question about the recent experimental evidence of Majorana edge states in topological superconductors. Which are the main differences between the experimental signatures of ...
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What is the temperature dependence of the critical current in weak links?

I am now working on hybrid Josephson junctions that are supposed to be tunnel junctions, so that the temperature dependence of the critical current should be $$ I_c ...
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Analogies between Fraunhofer diffraction and Josephson junctions

There are several analogies between diffraction patterns and Josephson junctions, especially between a double slit experiment and two Josephson junctions in a superconducting ring (like this): Both ...
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Cooper instability assuming triplet pairing

I am stuck on a question in Chapter 11 of Advanced Solid State Physics by Philip Phillips, which asks to do the Cooper instability calculation for triplet pairing. I attempt to solve the Schroedinger ...
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28 views

Does a superconducting coil need a minimum amount of electric current to be a superconducting magnet?

I'm not about that for a tiny amount of Cooper electrons perhaps we can't measure the magnetic field. I suppose that it needs some influental electric current below which the coil isn't a superfluid ...
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Will electron repulse by superconductor or at least change trajectory?

Suppose we have an electron gun which is bombarding superconductor. Would the electron get repelled or change its trajectory? It is well known that electrons are sources of magnetic fields. Also it ...
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82 views

Confusion between band structure and energy gap of conventional superconductor

Can anyone please clarify my confusion? Why does a superconducting state conducts electricity even if it has an energy gap? The difference between metals and insulators is that there is a gap at the ...
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95 views

Precisely speaking, does photon become massive or the phonon become massive, due to Higgs mechanism in superconductor?

Consider the low-energy field theories of superfluids and superconductors. In superfluids, the spontaneous breaking of the order parameter's phase creates phonons as the massless Goldstone ...
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37 views

Why does this 'Quantum Pinned' superconductor allow easy repositioning

I'm confused by videos such as this (popular demonstration of 'Quantum Levitation'): https://www.youtube.com/watch?v=Ws6AAhTw7RA So my current understanding of superconductors is that when in the ...
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103 views

How is the current equation calculated from Ginzburg-Landau (GL) free energy?

In the Ginzburg-Landau theory, we can get the current expression from GL free energy: $$F = \int dV \left \{\alpha |\psi|^2 + \frac{\beta}{2}|\psi|^4 + \frac{1}{2m^*} \mid (\frac{\hbar}{i}\nabla - ...
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What makes a superconductor topological?

I have read a fair bit about topological insulators and proximity induced Majorana bound states when placing a superconductor in proximity to a topological insulator. I've also read a bit about ...
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88 views

Relation between scattering matrix and an effective Hamiltonian

Could somebody provide the proof (or reference to some accessible literature) of relation $$S(E) = 1 + 2πiW^{†} (H_M − E − iπW W^{†} )^{−1} W \tag{2}$$ of arXiv:0806.4889, which relates $S$-matrix to ...
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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 ...
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Why are the Fermi levels of two different superconductors in a Josephson junction the same?

ELECTRON TUNNELING AND SUPERCONDUCTIVITY (Fig. 10A)– This is Giaever's Nobel lecture about how to measure the energy gap of each superconductor using a Josephson junction. I wonder why we can assume ...
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46 views

Why doesn't a levitating superconductor generate usable electricity?

Why doesn't a super cooled superconductor generate usable electricity due to the phenomenon of electromagnetic induction when placed upon a magnet? I basically mean, why can't it create electricity by ...
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137 views

Derivative of the magnetic field to the vector potential

So the magnetic field is defined with the vector potential A as: $$\mathbf{B}=\nabla\times\mathbf{A}.$$ How would I calculate the derivative: $$\frac{\delta}{\delta\mathbf{A}}|\mathbf{B}|^2$$ I ...
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157 views

Can one define wavefunction for Bogoliubov quasiparticle excitation in a superconductor?

Wavefunction is essentially a single particle concept. It is easily extended to multiparticle system as follows- if one has say five electrons the wavefunction of this five electron state is any ...
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53 views

Weinberg's QFT and superconductors

In the beginning of subparagraph about superconductors (which corresponds to paragraph about spontaneously symmetry breaking) Weingberg states that in superconductors EM gauge invariance is ...
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34 views

Meissner Effect for Para/Ferromagnetic substances

I read that Diamagnetism is a fundamental property of all materials, but it is relatively weaker, and is overridden by the stronger properties like Ferromagnetism. So is it possible, in theory, to ...
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56 views

Variation over complex function in Ginzburg-Landau theory

When deriving the Ginzburg-Landau equations, we minimize the following free energy over the complex function $\psi$: $$F = \int dV \left \{\alpha |\psi|^2 + \frac{\beta}{2}|\psi|^4 + \frac{1}{2m^*} ...
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19 views

how to measure a superconductor surface energy?

Surface energy, or interface energy, quantifies the disruption of intermolecular bonds that occur when a surface is created. In the physics of solids, surfaces must be intrinsically less energetically ...
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What can be found in the MT curves of superconductors?

I am confused about the magnetic susceptibility vs. temperature curves (MT) of superconductors (SCs). In the normal conduction state (I measured from 4.5K to 300K), the susceptibility curve can obey ...
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60 views

Is a superconductor perfectly opaque?

Because of the Meissner effect, no magnetic fields can pierce through the body of a superconductor. Since EM waves need both their electric and magnetic field components, it cannot pierce through the ...
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101 views

What makes Superconductor expel Magnetic lines of force?

What is it that causes the matter in superconducting state expel magnetic flux? What exactly happens at the atomic level which causes the expulsion of flux and super-conductance of electrons? Do all ...
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274 views

Can current be induced in a superconductor?

Moving a magnet close to a conductor induces a current. If it consists of a superconducting material with resistance $R=0$, then my textbook says: Then the induced current will continue to flow ...
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How can Multiple Andreev Reflections be explained as a succession of individual Andreev reflections?

I have understood the mechanisms at work in single Andreev reflections (N(ormal)-S(uperconducter) interface) and Andreev bound states (N-S-N). For multiple Andreev reflections of order 3, the ...
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What are the exact properties of a superconducting coil?

I've seen plenty of experiments involving a cylinder-shaped superconductor and a floating magnet. I haven't seen many, if any experimentation on the properties of coils. For example: Can we measure ...
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253 views

What symmetry class does 1D spinless $p$-wave superconductor belongs to?

$Z_{2}$ topological invariant exist for Kitaev model. What symmetries does it conserve? And to what symmetry class it belongs to? The hamiltonian for kitaev model can be written as $$ H=\sum_k ...
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Could spin waves be the cause of the pseudogap?

Could spin waves be the cause of the pseudogap and therefore be able to nudge the electrons in cuprate superconductors in a similar way that phonons (vibration waves) nudge electron in conventional ...
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47 views

Charge density waves: site-centering v.s. bond-centering

Question about charge density wave (CDW): From this Ref. page 13, why bond-centering charge density wave is naturally compatible with the observed coexistence of charge ordering and ...
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71 views

London equation and Maxwell equation

I am reading Tinkham's Introduction to Superconductivity (2nd ed) (Amazon link). On pages 4-5, they state that:" The second London equation 1.4, when combined with the Maxwell equation ${\rm ...
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34 views

flux quantization in super conductor

Magnetic force is a centripetal force. By that, we can make $$B = (h / \lambda r q) \, .$$ Is this flux quantization in superconductor ($h/q$)? If it is, is the wavelength of an electron the ...
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What theory describes high temperature superconductivity more sucessfully?

We know that there are so many theories on the high temperature superconductivity in cuprate. E.g. the U(1)/SU(2) gauge theory description of doped Mott insulator[Lee, Nagaosa, Wen], the phase-string ...
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3k views

What is the Difference Between a Type-1 and a Type-2 Superconductor?

As the title says, I was wondering what the difference was between a Type-1 and a Type-2 Superconductor. Especially in terms of the Coherent Length and Penetration Depth of a Magnetic Field - and how ...
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What is the Difference between a Lepton and a Fermion?

As the Title Says: I am Wondering what the Difference between a Lepton and A Fermion is. I know they both have an ½ integer spin number e.g. a electron, an atom with an odd mass number such as ...
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What happens to a superconductor when a magnetic fields strength increases?

I'm curious about what happens when a HTS is locked in place above a magnet via the Meissner Effect and say another magnet is added. Would the superconductors height fluctuate? Or would the extra ...
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What is the Difference Between BCS Theory and Ginzburg-Landau Theory?

What is the Difference Between BCS Theory and Ginzburg-Landau Theory? I have been studying Superconductivity and I know that Both of the theories (BCS Theory and Ginzburg-Landau Theory) can be used ...
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135 views

Origin of High-temperature Superconductivity

What is the mechanism that causes certain materials to exhibit superconductivity at temperatures much higher than around 25 kelvin?
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Rigorously prove that electric field is zero in a perfect conductor

I have ran into a problem while trying to prove that the electric field is zero in a perfect conductor My argument went something like this: We know that: $$\vec J = \sigma \vec E$$ In a ...
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Wave function of N electrons in a superconductor

Assuming that the wave function consisting of $N$ electrons is $\Psi_{N}(\bf{r_1,r_2,\cdots r_N)}$ then in the presence of a magnetic field ($\bf{B}=\nabla \times A$), how do I show that the current ...
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Nature of Cooper pairs

Some people say it is bound state, some say it is not. Which is more accurate? Problem is that I read in some books, including Ziman, that Cooper pairs are bound states but my teacher says that it is ...
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Why does Pressure Increase the Tc (Critical Temperature) of a Superconductor?

Just a heads up - please make this answer understandable to around 1st year degree level physics - not PhD research. So I can understand it - thanks. I was wondering why they Critical Temperature ...
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Introducing time-dependent drive into the Hamiltonian of quantised electric circuits

Suppose I have the schematic of a superconducting electric circuit composed of (quasi) lossless linear inductances and capacitances and some non-linear inductances, eg. Josephson junctions. The ...
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Why is the fermi surface of electron higher than the surface of hole in Iron-based superconductors?

I think the hole is higher than the electron in the brillouin zone, but the results of some experiments, like the ARPES, show the opposite results, why?
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287 views

How does current flow in superconductors if Cooper pairs have zero momentum?

I've been reading a lot of condensed matter textbooks, which state both that the net momentum of a Cooper pair in a superconductor is zero, and that Cooper pairs have momentum when they carry current. ...
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Real part of the AC conductivity has a discrete spectrum => What physics?

If the real part of the AC conductivity $\text{Re}[\sigma(\omega)]$ has a discrete spectrum only, i.e., $\text{Re}[\sigma(\omega)]=a_1\delta(\omega-\omega_1)+a_2\delta(\omega-\omega_2)+\cdots,$ what ...
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How to generalize BdG equation in order to match a graphene with a metal superconductor?

I want to generalize BdG equation in order to compute the conductance of a junction of graphene with a metal superconductor. The previous works done until now on this hetrojunction is devotted to use ...
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To what extent can the superconducting order parameter be thought of as a macroscopic wavefunction?

I know that the order parameter does not obey the Schrodinger equation; it instead obeys the Ginzburg-Landau equation. However, I am unclear as to the situations under which the view of the ...
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Superfluid rotating frame of reference

I'm currently studying a text about Bose-Einstein condensates (BECs) and vortices. When they want to study whether a vortex will be formed, they look at the fact wether it's enegetically favorable. ...