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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Does electric charge have any effect on diamagnetism?
Diamagnetic materials repel magnetic fields because freely moving electrons or cooper pairs within the material can form eddy currents in response to a changing magnetic field.
It is natural to wonder ...
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Current in a Superconducting Loop Interrupted by a Josephson Junction
Assuming we have the following circuit consisting of a superconducting loop having the same superconductor material everywhere, and interrupted by the short Josephson junction J1 with a phase ...
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Anderson Higgs mechanism and superconducting phase fluctuations
In the context of superconductivity, in the Anderson Higgs mechanism (see, for instance, https://doi.org/10.1119/1.5093291 (PDF), or https://doi.org/10.21468/SciPostPhysLectNotes.11 (PDF), the gauge-...
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Are there any known bulk superinsulators?
I recently learned about superinsulators. Basically materials which exhibit an abrupt phase transition to becoming perfectly resistive.
The wiki article reveals that this phenomenon is exhibited in ...
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How much liquid nitrogen is required for Maglev trains?
I understand magnets require cooling to achieve supermagnetivity. How much of liquid nitrogen do Maglevs carry with them? How much is required to keep them cool? What is liquid nitrogen consumption ...
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Expansion of interaction potential in terms of spherical harmonics in unconventional superconductivity
I am currently reading the book Introduction to Unconventional Superconductivity by V. P. Mineev and K. V. Samokhin. In Equation (1.6), the interaction potential $V$ is expanded in terms of spherical ...
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Josephson supercurrent measurement in a lab
This may be a very trivial question but I am a theoretician and can't find the answer to this question for the life of me. Is it possible to actually measure the Josephson supercurrent flowing through ...
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Is the superconducting wire in a equilibrium DC circuit free of surface charge?
Suppose we have a closed circuit composed of a time constant voltage battery, a resistor and superconducting wires connecting them in series. In the equilibrium state, both the free charge the ...
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Quasiparticle Density of States
In this paper we have the following:
The corresponding quasiparticle density is given by the equation
$$n_{qp} = 4N_0 \int_\Delta ^\infty dE \frac{E}{\sqrt{E^2 - \Delta^2}} f(E),$$
where $N_0$ is the ...
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Cuprate Superconductors parameters
What are the parameters for cuprate superconductors, is it the same with normal superconductors? Because I was wondering if the high temp and low temp makes the difference.
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What is Robert B. Laughlin saying about quantum field theory?
Robert B. Laughlin, A Different Universe states the following concerning the relationship between superconductivity and quantum field theory. I do not understand why he says "the microscopic ...
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How to know the relationship among the superconducitng phase , the gap, and the gapless edge states?
I feel puzzled about how to decide whether a material is in the superconducting phase, whether the gap can decide the superconducting phase, and whether there exists the gapless edge states.
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Spectral function of superconductor in the BEC regime: how does Higgs mechanism affect the spectrum?
Consider the standard BCS theory but assume that the interaction energy $U$ that enters the definition of gap parameter (i.e. $\Delta = (U/N)\sum_k \langle c_{-k\downarrow} c_{k\uparrow} \rangle$, ...
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Why superconducting qubits need periodic calibration?
I want to understand in some detail why superconducting qubits need periodic calibration. The usual, hand wavy explanation is environmental effects that tend to vary from time to time. However, I ...
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Cooper pair attractive power in lattice
In Kittel's book of Solid State Physics, it is said that, whenever an electron passes the positive ion core in the lattice, it has the ability to distort the lattice s.t by attracting the positive ion ...
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Can one Short a Hall Bar?
Consider a classical Hall bar, no quantum effects. If a magnetic field is applied the standard undergraduate treatment tells us that the Lorentz Force will lead to a build up of excess charge on one ...
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Modeling the difference between DC and AC current in a superconducting coil
I have an application I'm trying to model that involves using superconducting coils to produce a steerable dipole. To some degree, the problem is easier if I can modulate the current through the coil, ...
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Infinite conductivity, goldstone bosons and generalized voltage
Weinberg [1] has put forth an elegant argument (summarized in [2, Section 3.3] and at the bottom of the question), which suggests that the broken symmetry phase of any $U(1)$ gauge theory will be ...
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Phase difference in superconducting ring and gradient theorem
In Feymann's seminar on superconductivity there was this equation (21.28) $\oint_C\nabla \theta \cdot ds=\frac q \hbar\Phi$. Closed line integral $\oint_C\nabla \theta \cdot ds$ was claimed to be non-...
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Ideal Superconductor connected to Zero Voltage
If an ideal superconductor was just left alone, with no potential difference, what would be the current flowing in it?
According to Ohm's Law, $V = IR$
Hence, if a superconductor of $0\Omega$ ...
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Majorana zero modes in p-wave superconductors
I am trying to understand in an intuitive way why there is a zero mode in 2D p-wave superconductor with vortices (or in a similar model of He-A). Reading the paper by Misirpashaev, T. Sh, and G. E. ...
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Will a persistent supercurrent in a superconducting aluminum ring decay if the ring is connected to a non-superconducting aluminum wire?
Will a persistent supercurrent in a superconducting (SC) aluminum ring decay, if we connect the SC aluminum ring to an aluminum wire and the remote end of the wire is located in a separate chamber ...
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Lenz's law in supercoductors: What happens if a superconducting ring approaches a bar magnet?
Assume that the alignment of a bar magnet passes through the center of a superconducting ring. Can we say that if we accelerate the ring toward a pole of the bar magnet applying a force $F$, the ...
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Are there specific paths (tunnels) inside a superconductor for which any moving electron feels a zero net Coulomb's force?
I want to know what the zero electrical resistance of a superconductor means. Does it mean when we connect the terminals of a battery with a superconducting wire, the electrons move within specific ...
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Do superconducting materials have "zero" work function?
I understand that superconductors have zero resistivity, however, I wonder if there is a relation between resistivity and the work function of a specific material so that a superconductor has zero (or ...
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Some references on Dh4 point group ans superconductors
Just wondering if anyone has any lecture notes or books/chapters which cover the representations of Dh4 CLEARLY. In particular, the form factors of superconductors are labeled with the representations ...
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Link between the charge and the phase in a superconducting circuit
I have a question related to superconducting quantum circuits. Especially regarding the derivation of the transformation of $\cos(\phi)$ in the charge basis.
In this question, a user states that ...
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Infinite series of diagrams = one-loop RG equations？
In the RG of $\rm Fe$ based superconductor, the author wrote something like Infinite series of diagrams (RPA)= one-loop RG equations.
I wonder if it is a universal theorem.
I don't have a background ...
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Is it possible that when measured more than one Cooper pair will have tunneled across the junction?
If I've understood the idea correctly a charge qubit is formed by a superconducting island coupled by a Joseph junction to a superconducting reservoir. The state of the qubit is determined by the ...
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Ambiguities of the Hubbard-Stratonovich decoupling
Consider an interacting fermionic theory on some lattice $\Lambda$ with action
$$
\mathcal{S}[\bar{\psi},\psi] = \int_{0}^{\beta} \mathrm{d}\tau \sum_{i\in \Lambda} \sum_{\sigma = \left\{ \uparrow,\...
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Kink in Dispersion Relationship due to Electron Phonon Coupling
How can I start from a Hamiltonian with electron-phonon coupling and show that a kink should show up in the energy dispersion relationship?
In a brief communication called "Universal Nodal Fermi ...
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Why Zeeman coupling can be used in Bogoliubov-De Gennes superconducting Hamiltonian and Josephson junctions model for Majorana?
It is well-known that type-1 superconductivity holds perfect diamagnetism, which means that magnetic field is expelled by the superconductor.
However, there are cases, especially in the topological ...
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LK-99 a total waste? [closed]
It looks like LK-99 is not what it was purported to be. Disappointing but not surprising.
However did anything of substance or new ways or approaching the problem brought to light in the way it was ...
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How to understand charge-$4e$ superconductivity?
Why might electrons exhibit a preference for forming a charge-$4e$ condensate, as opposed to the conventional BCS charge-$2e$ condensate? Could superconductivity potentially arise from pairings within ...
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Waveguides: Coplanar Strips vs. Coupled Microstrip line design advantages disadvantages & characteristic impedance (superconducting waveguide)
I am very much new to waveguides and I am struggling to calculate the characteristic impedance of my coupled microstrip design. I am using niobium for the electrodes and for the Coplanar Strips I ...
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How does magnetical energy comes in superconducting phase transition
Show me this is not a perpetual motion machine.
Step 1. Put a superconducting material in a strong magnetic field.
Step 2. Cool down the superconducting material
Step 3. It levitates
Step 4. Heat ...
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Superconductivity vs. energy gap
Many textbooks derive the single-particle excitation energy gap from the BCS mean-field hamiltonian, and then stop there, implying that this gap is sufficient for superconductivity.
To be frank, I ...
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How can Cooper pairs be stable?
In the BCS theory, a Cooper pair is formed by two electrons of nearly opposite momentum $(k \sim -k')$. What I don't understand is how can this structure remain stable in the metal:
Assume that the ...
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LK-99: Are all conductive strong diamagnets superconductors?
Motivated by the LK-99 material story lately, which seems to me to behave under an external magnetic field more like a strong diamagnetic compound and according to the inventors it is also ...
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Diquark propagators in color superconductivity
I’m studying color superconductivity referring to “The Phases of Quantum Chromodynamics From Confinement to Extreme Environments” by John B. Kogut and Mikhail A. Stephanov (link).
In chapter 9, the ...
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What are the two basic experiments to identify different phases in high $T_c$ cuprates systems?
what are the two basic experiments to identify different phases like antiferromagnetic, pseudogap, superconducting, strange metal and fermi-liquid in high $T_c$ cuprates systems like BSCCO and YBCO?
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Ductility of LK-99
I’ve heard about the new proposed superconductor known as LK-99, one thing I’m wondering that I haven’t yet gotten an answer to is how ductile is it? I.E. how easy would it be to make wires out of it?
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Would there be a split between ZFC and FC in a type-I superconductor?
I am trying to understand why there is a split between ZFC and FC in superconductors. I found an answer that suggests that some flux remains in the superconductor after cooling. However, according to ...
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Does a levitating super conductor (Meissner effect) add weight?
A platform is placed on a weight scale. The scale reads 1kg. A super conductor weighing 100g is placed on top of the platform and it levitates such that no physical contact is made to the platform. ...
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Josephson current operator and conjugate variables
I am studying multi-terminal Josephson junctions and encountered the formula
\begin{align}
\hat{I}_{\alpha} = \frac{2e}{\hbar}\frac{\partial\hat{H}}{\partial\phi_{\alpha}}
\end{align}
where $\hat{I}_{\...
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Can we derive the equation of motion of superconductor in this video?
Recently, I tried to understand the effect of Quantum levitation. I read that there is some well-known fact: Relative distance between superconductor and magnet must be preserved, because of flux ...
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Why haven't we found thermal superconductors?
First of all I want to apologize if this is a stupid question. I'm a layman who's merely very interested in physics, without a degree to my name.
I was trying to research electric superconductors ...
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Is it possible to combine aerogels and superconductors? would it levitate?
I read a previous question "superconductor levitating in earth's magnetic field?"
it seemed like the impact of gravity would make this unikely unless the superconductor was super light.
Is ...
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Why does flux pinning prevent a superconductor from moving
I've seen this answer, which clarifies that superconductors float on top of permanent magnets not because of the Meissner effect, but because of flux pinning. The superconductor is cooled, and in that ...
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Are all materials that have 0 electrical resistance superconductors?
Are all materials that have 0 electrical resistance superconductors?
Are all perfect diamagnets superconductors？
