1. Graduate Lecture Series
29 June – 3 July, 2009
Prof Ngee-Pong Chang
Lecture 5
Superconductivity
Flux Quantization
&
SQUID

2. Kammerlingh Onnes
On the Sudden Rate at Which the Resistance of Mercury Disappears
Communications of the Leiden Laboratory, 1911

3. Onnes-Holst measurement of Hg resistance
Onnes-Holst measurement of Hg resistance

4. Meissner Effect 1933 Robert Ochsenfeld
Walther Meissner

5. Inside sphere

6. Superconductivity

7. Drude’s Theory of Conductivity
Perfect conductor
Limit

8. London’s Equations London’s Equation London’s Equation Superconductor
Is better than
perfect conductor
London’s Equation
London’s Equation

9. London Equations
Fritz London

10. Proc Roy Soc A149, 71, 1935

11. Maxwell’s Equations for Superconductor

14. http://web. mit. edu/6. 763/www/FT03/Lectures/Lecture17

15. http://web. mit. edu/6. 763/www/FT03/Lectures/Lecture17

16. BCS Theory of Superconductivity
John Bardeen
Leon Cooper
John R. Schrieffer
BCS Theory of Superconductivity
Phys.Rev.108, 1175 (1957)

17. In Absence of Magnetic Field Cooper Pair has zero momentum
Superconductor Charge Density
In Absence of Magnetic Field
Cooper Pair has zero momentum

18. In absence of Magnetic Field In presence of Magnetic Field
momentum
In presence of Magnetic Field
momentum

19. In the Presence of Magnetic Field Cooper Pair with zero momentum

20. Superconducting Current
charge density is constant
phase depends on vector potential
Superconducting Current
Superconducting current

21. Quantization of Flux

22. Deep inside

23. Deep inside
fluxoid

24. Fluxoid Quantization B.Deaver & W. Fairbank Phys Rev Lett 7, 43 (1961)

25. Brian D. Josephson
1940 -

26. Vo I II

27. Vo I II

30. Josephson Current

31. Anderson & Rowell experiment, 1963
D.C. Josephson effect
Anderson & Rowell experiment, 1963
For V ≠ 0 , JDC = 0
For V = 0 , JDC = Jo sin δo
P.W. Anderson

32. A.C. Josephson Current

33. A.C. Josephson Current

34. Coupled Josephson Junctions in an external magnetic field
SQUID a Ca P Q Cb b
Coupled Josephson Junctions in an external magnetic field

36. SQUID current for general FluxCa P Q Cb b

37. SQUID

38. SQUID Biomagnetic Device

43. Look to the Galaxies

44. Is terrestrial physics different than celestial ?

46. 10-12 August, 2005
Nanyang Technological University National University of Singapore Biopolis, A*STAR