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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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38 views

If I apply a position dependent temperature gradient to a s wave superconductor, would I get a position dependent superconducting order parameter?

What would happen if a s wave superconductor placed in a position dependent temperature gradient, where $T(x)<T_c$ is always satisfied. Would I get a position dependent superconducting order ...
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124 views

Why a superconductor expel magnetic lines of force from inside completely when cooled below critical temperature?

Suppose a superconductor which is in a normal state (i.e. $T>Tc$) is subjected to a magnetic field. As soon as magnetic field switched from 0 to some value, eddy currents will develop on the ...
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Does zero resistance mean that there are no energy exchanging processes between particles in superconductor? [closed]

I was just knowing little bit about bose einstein condensate then I came across superconductor. In the bose einstein condensate particles have same energy levels and they can not escape the level or ...
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Transmons and cooper pair box qubits: two islands or a single island and a reservoir

In scientific literature, one typically describes Cooper pair boxes as a small superconducting island coupled to a superconducting reservoir (say, a large ground plane of superconducting metal, or a ...
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65 views

Faraday's law superconducting [duplicate]

When we say flux can't be changed through superconducting coil , because resistance is zero , So this implies there is no induced emf in the coil , If it is so what makes current flow in the coil ...
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247 views

How many types of phonons are there, and what are their characteristics?

I've skimmed through Wikipedia's article, as well as as PSE question What is a phonon?, but I am still entirely left in confusion as to the types of phonons and their corresponding characteristics and ...
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248 views

Is the Bogoliubov quasiparticle boson or fermion?

The Bogoliubov quasiparticle combines the properties of a negatively charged electron and a positively charged hole, so here we have two fermion and the quasiparticle have an integer spin. By this ...
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43 views

What is the point in discovering a material that is superconductor at very low temperatures?

From my understanding what is really relevant is to obtain superconductivity at high temperatures, as close as possible to standard conditions of pressure and temperature. So, what makes materials ...
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Tunneling junction in electromagnetic field [closed]

Why in presence of electromagnetic field hamiltonian,describing 2 systems with tunneling(for example josephson junction ) $$H=H_L+H_R+T(I+I^{\dagger})$$ where $I=c_Lc^{\dagger}_R$ is tunneling ...
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39 views

Using superconducting coils as a transformer

In experiments such as tokamaks, typically an ohmic transformer (primary) is used to produce current in the plasma (secondary) by swinging from to the most positive to negative magnetic field. Ideally ...
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48 views

Ginzburg-Landau boundary condition in the 1D no fields case

It is commonly seen that in finding the coherence length from Ginzburg-Landau, that the following equation is found: $\frac{\partial^2 f}{\partial \eta^2} + f(1-f^2) = 0$ which is for a superconductor ...
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417 views

Equation for kinetic inductance and the Mattis Bardeen Formula

I've been reading Tunable superconducting nanoinductors by Annunziata et al. 2010 which is a paper in which they construct inductors from ultra-thin, approximately 100 nm wide strips of niobium (Nb) ...
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the origin of flux pinning force in mixed state of a superconductor

The flux lines tends to get pinned at the imperfections present in the material, called as pinning centres. But what is the origin of that pinning force, which holds the flux lines at such sites
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The free energy expansion in terms of order parameter in GL theory

Please check the image provided. If somebody can explain why the last two terms were considered and how it happened to be so. According to some text books, its because of expulsion of applied field by ...
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Formulating BCS theory in the functional integral with a real order parameter

Often in BCS theory, people take the order parameter $\Delta$ to be real. I tried to construct a BCS theory with a real order parameter from the start and ran into some trouble. I'd be interested to ...
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What “transformations” did Abrikosov use in 1958 to get the famous $11-2\log{2}$ result in fermi-liquid theory?

How does one obtain the final integral expression in the appendix of Abrikosov and Khalatnikov's 1958 paper: $\ \ \ $ "Concerning a model for a non-ideal fermi gas" $\ \ \ $ ??? Below, in Bold, I ...
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Metallic state in 2D

Mermin Wagner theorem prevents any spontaneous breaking of continuous symmetry for short ranged interactions for dimensions, D $\leq$2 for any finite temperature. So I understand that superconducting ...
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Why do microwave ports for superconducting qubits look the way they are?

Often you see input/output ports for superconducting qubits looking like this block, which tapers down to a narrow transmission line: what is the reason for this tapering, and how do you actually ...
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Does the penetrating magnetic field lines affect the Eddy currents cancellation of an exterior magnetic field?

If a Type-II superconductor's surface is placed near a resistive wire, and current($I$) is applied, during a short duration of time while the current is reaching steady state, the magnetic field of ...
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29 views

Current-current correlator in superconductivity

I was reading a paper on superconductivity. There is a claim that if the momentum space current-current correlation function $\langle\mathcal{T} j_{\mu}(k)j_{\nu}(-k) \rangle$ has a pole at zero ...
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52 views

Vortex motion in superconductors

In mixed state of a type-II superconductor, when we allow a transport current to pass through it, we say that the Lorentz force acts and as a result the flux starts flowing, when the force is greater ...
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band gap (or energy gap) relation with discontinuity on spceific heat

Is change in band gap or energy gap with respect to temperature, reason behind the discontinuity in specific heat data as in case of superconductors?
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Superconduction current due to diamagnetism and induction

If we cool a superconductor S below it's critical temperature while a magnet is resting on top of it, an electric current I1 will develop on it's surface to expel de magnetic field. Now let us suppose ...
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199 views

Faraday's law in superconducting loop

Let's say that you have a superconducting loop (resistivity=0 exactly) whose area is increasing in a uniform non-changing magnetic field. Obviously there will be a CHANGING flux associated with the ...
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69 views

Can cooper pairs form in the absence of any external magnetic field?

Let us cool a superconductor below its critical T in the absence of any external magnetic field. No electric current will flow. Though there is no current, are there cooper pairs ? Thanks
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Connection between theory of superconductivity and Bohmian mechanics

I stumbled upon an interesting chapter of Feynman Lectures about Superconductivity and was surprised to see that the equations of motion of the superconducting electron fluid (21.38 and 21.39) hold a ...
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64 views

Why do Spin Density Waves form?

can someone tell me if there is an intuitive picture why electrons form Spin Density Waves (SDWs), if the charge density diverges? I know that in 1D there is a divergence in the electronic ...
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381 views

Zero Ohmic resistance in superconductors is a little bit too enthusiastic?

According to this article: Superconductors contain tiny tornadoes of supercurrent, called vortex filaments, that create resistance when they move. Does this mean that our description of zero Ohmic ...
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Is there any positive temperature from which superconductivity ceases?

From what I understand about superconductivity, it is due to a coupling between Cooper pairs and phonons. At the absolute 0, there is no phonon, so I assume superconductivity cannot exist at that ...
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308 views

Reason for a Cooper “Pair” Formation

I'm an Australian high school student (Grade 12). We are currently covering superconductors as a topic for our syllabus. Can someone explain (inasmuch as an advanced 18-year-old physics student can ...
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167 views

High-temperature superconductivity

Is high-temperature superconductivity explained with the same argument as the low temperature one? What is the maximum temperature reached? What about Room-temperature superconductors?
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Does current in a superconducting circuit ever decay?

Once a current has been started in a superconducting loop, say by induction, will it truly stay on forever or is it intrinsically doomed to decay, albeit slowly? For example, can radiative losses ...
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770 views

London theory, an electromagnetic description?

Currently I'm reading "Introducton to Solid-State Physics" by Charles Kittel, 8th edition and about superconductivity. I'm having a bit of trouble getting the whole plot, because as far as I'm ...
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Why quantum computing companies use superconducting qubits? [closed]

Why are superconducting qubits superior to other types of experimental realisation of qubits? I assume this because Dwave, IBM, rigetti among other companies in the quantum computing business use ...
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29 views

High-dimensionality of multi-electron wavefunctions

My understanding is that the main difficulties in understanding superconductivity and topological insulators is related to the fact that free electrons are highly entangled and models that simplify ...
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Can a superconductor have a Fermi surface in its superconducting state?

In the superconducting state, there are Cooper pairs instead of free electrons, so there is no Fermi surface. Is this always true, especially when there are charge density waves? Is it possible that ...
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Forces in a quantum levitation

When a superconductor is quantumly levitated, what are the forces experienced by the superconductor and magnet?
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Magnetic Field Strength and a Spherical Superconductor

While reading through notes of a class I am taking, I came across an example exercise about a superconducting sphere in an applied magnetic field. In this example it states the following: \begin{...
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General questions on the superconducting order parameter

Regarding the concept of singlet and triplet superconductor. In the very good answer to the question What is a $p_x + i p_y$ superconductor? Relation to topological superconductors the answerer says ...
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Why don't currents in Superconductors lose energy as light?

We are told that in superconductors, there is no internal resistance. So if a current is induced in a superconducting material (like an Eddie Current), it should theoretically flow forever (or until ...
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52 views

Why is current and not voltage varied for a Superconductor?

I am an undergraduate physics student and recently undertook an experiment in which the resistance of a superconductor, and a semiconductor, was investigated at different temperatures. The resistance ...
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How to approximate a retarded interaction by an instantaneous one?

I'm now having a retarded interaction (in terms of imaginary time) of the form: $$-\frac{1}{2\mathcal{V} \rho_{\varphi}}\int d\tau_{1}d\tau_{2}\sum_{k,k'}\frac{1}{2\Omega_{k-k'}} e^{-\Omega_{k-k'}|\...
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61 views

Two-body bound state in 3D

I was reading a lecture note, where it talks about the two-body bound state in 1D, 2D and 3D. It says that, in 1D or 2D situation, two particles with any arbitrary attractive interaction, can form a ...
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hybridization integral and energy barrier in high-temperature superconductor cuprates

I am reading an article about high-temperature superconducting cuprates. It was saying because the hybridization integral $t_{dp}$ is much smaller than the energy barrier E$_p$-E$_d$, the electrons in ...
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How are the assumptions for the deduction of thermodynamics properties consistent with each other?

I am looking at the deduction of thermodynamics properties, specific heat, entropy, enthalpy, and Gibbs free energy, in presence of a magnetic filed $\mathrm{B}$ of Superconductors, following the book ...
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148 views

What factors affect the critical temperature of a material?

I recently started learning electricity in A level physics and came across the concept of superconductivity. I find this very intriguing due to its capabilities. My questions are: What are the ...
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83 views

Superconductors and conservation of angular momentum

One of the diagrams in my textbook show a superconductor in a magnetic field along with some arrows over it which presumably indicate current. Also all the current arrows seem to be pointing in one ...
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71 views

A Question related to energy losses in superconductors

When we look at a superconductor, the conductivity is infinite. And when we apply a potential difference across the ends of the superconductor, the electrons have to start accelerating because there ...
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61 views

How can i maintain a temperature of 5k on a super conducting wire?

I have bought nb/ti low temperature superconducting wire , so i can make a superconducting magnet, my liquid nitrogen supplier is ready to meet my needs but , i need to maintain that temperature in ...
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211 views

What determines the direction of current in a superconductor

Type I superconductors have no electric field nor magnetic field inside of them, when they are in the superconducting state. This means no voltage difference across any two points or regions inside of ...