# 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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### How to derive the wavefunction for a $p$-wave superconductor?

I would like to understand the steps for deriving the spatial wavefunction for $N$ fermions in the $p$-wave BCS ground state. In this paper, they derive the BCS ground state (Equation 11, though I ...
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### How do Experimental Condensed Matter Physicsts find Interesting Material

In general, this question is "how much material science does a condensed matter theorist need to know and how do I learn?" More precisely, as a condensed matter theory PhD student, I am ...
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### Josephson Junction - characteristic Impedance

Currently, I am working on antennas connected to a Josephson Junction to detect terahertz radiation. The junction shows a normal state resistance $R_n$ of approx. $0.9~\Omega$. To simulate the ...
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### Superinsulator infinite voltage

Everybody knows about superconductivity, at cryogenic temperatures conductor resistance drops to zero for direct current. There is lesser known related phenomena called superinsulator where material ...
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### Diagonalizing the BCS model as a Gaudin model

I've been looking at the BCS model through a few papers (listed at the bottom). I'm having trouble with many things but I think I've boiled it down to a few: -- In the first paper below (Ortiz), the ...
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### Johnson noises in the Josephson junction based devices

I have difficulty understanding that superconductors being non-dissipative; have resistive noises. Even if we consider the case of charge noise and minimal thermal noises (if present) how can we ...
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### Is superconductor just a perfect conductor or anything more than that?

If I had a hypothetical perfect conductor having infinite conductivity and I cool it below a certain temperature, will it be a superconductor? If not, then how can we distinguish between the two using ...
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### Entanglement spectrum of a superconductor

Consider the Hamiltonian $$H = \sum_{k} \epsilon_k c_{k}^{\dagger} c_{k} + (\Delta_k c_{k}c_{-k} + h.c.)$$ where $\epsilon_k$ and $\Delta_k$ are that of p-wave superconductor. So we have ...
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### BCS Theory: Bogoliubov Transformation for Fermions

I would like to follow up on this question. The Bogoliubov transformation is written as follows (I assume that $u_{\mathbf{k}} = u_k$ and $v_{\mathbf{k}} = v_k$ as well as $u_k, v_k\in\mathbb{R}$): \...
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### Phase-Number Uncertainty in the extreme cases

I'm trying to understand the phase-number uncertainty relation for superconductors, \begin{align} \Delta N \Delta \varphi \gtrsim 1. \end{align} In particular, I'm trying to understand if it holds for ...
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### What is the role of Fermi level in a superconductor? How will you understand the Fermi level in a superconductor?

What is the role of Fermi level in a superconductor? How will you understand the Fermi level in a superconductor? Distinguish between the Fermi level of a metals and superconductors?
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### Can you distinguish between different materials by looking them visibly if you have metals, semiconductors and superconductors?

Can you distinguish between different materials by looking them visibly if you have metals, semiconductors and superconductors?
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### Infinite current density inside superconductor

Context: It is commonly stated (such as in Tinkham's "Introduction to Superconductivity") that the current in a superconducting wire is concentrated in a layer around the surface of ...
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### Critical Field outside the Meissner limit - derivation

In Tinkham's "Introduction to Superconductivity" Second Edition, Chapter 2.2.1, the author states that ... the superconducting state becomes energetically unfavorable above the magnetic ...
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### Magnetic Field at the interface and around a superconductor

In Tinkham's "Introduction to Superconductivity" Second Edition, Chapter 2.2.1, the author discusses the problem of a superconducting slab in a uniform external field. In the solution ...
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### Zero of energy and chemical potential in a superconductor

I am having trouble grasping some concepts related to how energy is measured in a superconductor. In BCS theory, we are given the energy of the quasi-particles as $E = \sqrt{\varepsilon^2 + \Delta^2}$ ...
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### Vector identity and Electric Field Screening in Tinkham's

I'm going through Tinkham's "Introduction to Superconductivity" Second Edition. In Chapter 2, the author states that "we obtain \begin{align} -\nabla \times \nabla \times {\bf E} = \...
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### How do you translate from separate vector potential gradients to magnetic field components?

In an attempt at calculating anisotropic London penetration depths, I have obtained equations of the form  \begin{split} -\mu_0^{-1}\nabla^2B_x &= Z\partial_yA_z - T\partial_zA_x-Y\partial_zA_y,\...
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### Why does triplet pairing not have line nodes on the fermi surface when spin-orbit coupling is present

I have read that in the presence of spin-orbit coupling, triplet pairing superconductors "in general" do not have lines nodes on the fermi surface (e.g., ,) under symmetry properties, ...
### Can phonons induce non-$s$-wave superconductivity?
In BCS theory the interaction is considered isotropic and the result is an $s$-wave superconductor. Is it possible anyway for unconventional superconductors to have SC driven by phonons (I intend this ...