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J. J. Strossmayer University in Osijek Bachelor of science Thessis Department of Physics FENOMENOLOŠKA TEORIJA SUPRAVODLJIVOSTI DANIJEL PEROVIĆ 46
5. ABSTRACT : In this work, we study the remarkabel phenomenon of superconductivity. These theories were suprisingly accurate and profoundly influenced the present many-body theory of superconductors. The later ( BSC ) theory represents one of the most successful applications of many-body techniques; in addition to its new predictions, it also justifies the earlier descriptions and allows an evaluation of the phenomenological constants. Basic experimental facts: Infinite conductivity: When any one of a large class of metallic elements or compounds is cooled to within a few degrees of absolute zero, it abruptly losses all trace of electrical resistivity at a definite critical temperature T c. As a first approximation, we assume the usual constitutive equation ( Ohm'¨s law ) r r j = σE A combination with Maxwell's equation ∂B r = − curlE ∂t Meissner effect: When the sample is cooled and become superconducting, experiments first first performed by Meissner and Ochsenfeld demonstrate that all magnetic flux is expelled from the interior. Note that this results does not contradict the previous conclusion of constant B in the superconducting state; rather it indicates that the constant value must always be taken as zero. Critical field: For simplicity, we consider a long cylinder of pure superconductor in a parallel appplied field H, where there are no demagnetizing effects. If the semple is superconducting at temperature T in zero field, there is a unique critical field H c ( T ) above which the sample become normal. H c ( T ) = H ( 0) c ⎡ ⎛ ⎢1 − ⎜ ⎢⎣ ⎝ Persistent currents and flux quanti<strong>za</strong>tion: as a different example of magnetic behavior, consider a normal metallic ring place din a magnetic field perpendicular to its plane. When the temperature is lowered, the metal becomes superconducting and expels the flux. Suppose the external field is then removed; no flux can pass through the T T c 2 ⎞ ⎤ ⎟ ⎥ ⎠ ⎥⎦ 47
Page 1 and 2: SVEUČILIŠTE JOSIPA JURJA STROSSMA
Page 3 and 4: Sveučilište J. J. Strossmayera u
Page 5 and 6: Sadržaj: Uvod…………………
Page 7 and 8: 1.1 . Ovisnost supravodiča o kriti
Page 9 and 10: 1. Teorija supravodljivosti: 1.1. O
Page 11 and 12: 1.4. Ovisnost električnog otpora o
Page 13 and 14: 1.1.2. Energetski procijep: Elektro
Page 15 and 16: Dolazimo do zaključka da se u unut
Page 17 and 18: ne 2 τ &r ∇ × j = − B m Nakon
Page 19 and 20: B y = By0 e − x a Promjenom druge
Page 21 and 22: 1.2. MIKROSKOPSKO OBJAŠNJENJE SUPR
Page 23 and 24: Elektron koji je izazvao deformacij
Page 25 and 26: 1.2.4. JOSEPHSONOV EFEKT: B. Joseph
Page 27 and 28: U Josephsonovu spoju Cooperovi paro
Page 29 and 30: 1.13. Izmjenični Josephsonov efekt
Page 31 and 32: Supravodiči II. tipa dani su u tab
Page 33 and 34: negativna ako je ξ< λ L . Ako je
Page 35 and 36: tj. ovisi o susceptibilnosti tijela
Page 37 and 38: magnetskog toka za 1 kvant (flukoso
Page 39 and 40: može izbjeći postojanje centra ra
Page 41 and 42: 3.2. Viskotemeparturni supravodiči
Page 43 and 44: 3.1. Supravodljivost kroz Nobelove
Page 45: 5. ŽIVOTOPIS: Zovem se Danijel Per

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