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GATE 2022 PH – Question 44

Solid State Physics · superconductivity: type-I and type II superconductors, Meissner effect, London equation, BCS theory, flux quantization. · 2 marks · Multiple choice

At T = 0 K, which of the following diagram represents the occupation probability P(E) of energy states of electrons in a BCS type superconductor?

Candidate BCS electron occupation curves.
  1. Option A in the figure
  2. Option B in the figure
  3. Option C in the figure
  4. Option D in the figure

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Show answer and explanation

Correct answer: (A) Option A in the figure

Explanation

The BCS occupation is $v_k^2=(1-\xi_k/\sqrt{\xi_k^2+\Delta^2})/2$, smoothly falling across the Fermi energy even at zero temperature.