Superconductor physics notes for exam Preperation, Study notes of Physics

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➢ Type 2 superconductors are characterized by two critical magnetic fields 𝐻𝑐 1 (lower critical field) 𝑎𝑛𝑑 𝐻𝑐 2 (upper critical field) ➢ For the applied field strength less than critical field 𝐻𝑐 1 , material expels the magnetic field completely and behaves as perfect diamagnet from end to end. When H exceeds 𝐻𝑐 1 , the flux penetrates the body and fills in partially ➢ This state between 𝐻𝑐 1 and 𝐻𝑐 2 Is called vertex state. ➢ The flux penetration occurs through small channelized parts of the body called filaments. ➢ Though there is flux penetration the material retains its zero resistance property ➢ With further increase in H, flux penetration increases there by decreases the diamagnetic part of the body. ➢ When H > 𝐻𝑐 2 ,the material turns into normal conductor. ➢ Type 2 superconductors have very high value of 𝐻𝑐 2 ➢ Hence they are useful in building devices working with high magnetic fields ➢ They are also called hard superconductors

• The phase difference between the two paths 𝛿𝑎 𝑎𝑛𝑑 𝛿𝑏 is 𝛿𝑎 − 𝛿𝑏 =0 in the absence of the field.
• When the magnetic field is applied in the perpendicular direction 𝛿𝑎 − 𝛿𝑏 ≠ 0