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.

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

Superconductivity was first observed by Kamerlingh Onnes in 1911 when he discovered that the resistivity of mercury went to zero at $4.2 \ \text{K}$. Since that first discovery, superconductivity has been found in a wide variety of material classes, from pure elements to complex structures like cuprates, organometallics, and heavy fermions. The current record for high-temperature superconductivity is close to $150 \ \text{K}$, which is found in a cuprate compound at high pressure.

Important outstanding questions in superconductivity research remain the origination of the pairing mechanism for unconventional superconductors and whether room temperature superconductivity is possible.

There are many web resources for superconductivity. General introductions to the topic may be found on the following websites:
Hyperphysics: http://hyperphysics.phy-astr.gsu.edu/hbase/solids/scond.html
Wikipedia: https://en.wikipedia.org/wiki/Superconductivity.

The current research edge of the field may be found on the arXiv preprint server, which has an entire subsection devoted to superconductivity research: https://arxiv.org/list/cond-mat.supr-con/recent

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What is a $p_x + i p_y$ superconductor? Relation to topological superconductors

I often read about s-wave and p-wave superconductors. In particular a $p_x + i p_y$ superconductor - often mentioned in combination with topological superconductors. I understand that the overall Cooper pair wavefunction may have orbital angular…
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Why is high temperature superconductivity so hard to solve?

The phenomenon of high temperature superconductivity has been known for decades, particularly layered cuprate superconductors. We know the precise lattice structure of the materials. We know the band theory of electrons and how electronic orbitals…
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Should a superconductor act as a perfect mirror?

I have been told that metals are good reflectors because they are good conductors. Since an electric field in conductors cause the electrons to move until they cancel out the field, there really can't be electric fields in a conductor. Since light…
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How can Ohm's law be correct if superconductors have 0 resistivity?

Ohm's law states that the relationship between current ( I ) voltage ( V ) and resistance ( R ) is $$I = \frac{V}{R}$$ However superconductors cause the resistance of a material to go to zero, and as I understand it, as $R \to 0$, $I \to \infty$.…
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Why don't superconductors, which have zero electrical resistance, violate the second law of thermodynamics?

There are bunch of questions on here asking whether superconductors really have exactly zero resistance and answers saying they do. My question is how this doesn't violate the second law of thermodynamics, which, if I understand correctly, implies…
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Do topological superconductors exhibit symmetry-enriched topological order?

Gapped Hamiltonians with a ground-state having long-range entanglement (LRE), are said to have topological order (TO), while if the ground state is short-range entangled (SRE) they are in the trivial phase. The topological properties of a system…
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Are room temperature superconductors theoretically possible, and through what mechanism?

At the moment, the highest critical temperature superconductor known to science (or myself, at least) is mercury barium calcium copper oxide. With a $T_{c}$ of roughly 133 K, that's well above the boiling point of nitrogen, and even well above the…
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Mean field equations in the BCS theory of superconductivity

In BCS theory, one takes the model Hamiltonian $$ \sum_{k\sigma} (E_k-\mu)c_{k\sigma}^\dagger c_{k\sigma} +\sum_{kk'}V_{kk'}c_{k\uparrow}^\dagger c_{-k\downarrow}^\dagger c_{-k'\downarrow} c_{k'\uparrow} $$ This Hamiltonian clearly conserves…
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Why is there a band structure for strongly correlated systems?

The existence of band structure of a crystalline solid comes from the Bloch theorem, which relies on the independent-electron approximation. Why do people still talk about the band structure for a strongly-correlated system, e.g. superconductors and…
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Is an electron a superconductor?

A superconductor has zero resistance. What about an electron in a vacuum? Could this simple system be considered superconducting?
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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 cuprates being related to topological…
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What is the link between the BCS ground state and superconductivity?

The link between the BCS ground state $$ \left|\Psi_\mathrm{BCS}\right\rangle = \prod_k \left( u_k - v_ke^{i \phi} c_{k\uparrow}^{\dagger} c_{-k\downarrow}^{\dagger}\right) \left|0\right\rangle $$ and the property of superconductivity (carrying…
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What observables are indicative of BCS Cooper pair condensation?

What observables are indicative of BCS Cooper pair condensation? "Thought" experiments and "numerical" experiments are allowed. This question is motivated by the question Has BCS Cooper pair condensate been observed in experiment? , and by our…
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Superconductor symmetry breaking

When water freezes continuous translational symmetry is broken. When a metal becomes superconducting, what is the symmetry that gets broken?
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Intuitive reasons for superconductivity

Superconductivity I read in a book "Physics - Resnik and Halliday" the explanation of Type-I Superconductors {cold ones} that: The Electrons that make up current at super-cool temperatures move in coordinated pairs. One of the electrons in a pair…
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