# Tagged Questions

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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### Why do superconductors have a maximum current density?

If superconductors have no resistance, what prevents you making the cross-section as small as you can handle, if there will be no power dissipated anyhow? Is there a limit on the magnetic field that ...
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### Superconducting Order Parameter and Time Reversal Symmetry

How to understand the following definition of a time reversal operation $K$ given in the review by Sigrist and Ueda: $$K a_{\mathbf{k},s}^{\dagger} = \sum_{s'} (-i\sigma_y)_{s,s'} a_{-\mathbf{k},s'}$$ ...
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### 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 ...
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### Is there an electric field within a superconducting inductor?

I have learned that the magnitude of the EMF (potential difference) between the terminals of an inductor is equal to L*di/dt. Does this imply that an electric field does indeed exist in an ideal ...
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### If BdG Hamiltonian has particle-hole redundancy, how can it be trusted in discussing the topological properties of superconductors?

In BdG Hamiltonians, the particle-hole symmetry is not a true symmetry but rather a redundancy of description. In my oppinion, saying with the presence of particle-hole symmetry is just saying: hey, ...
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### Earth's magnetic field

New researchs found that very high pressure on certain materials may reduce the degree of temperature required to change to superconductor. So is it possible that the high pressure in earth core ...