1. To resolve the mystery of superfluidity and supersolidity: superfluidity as a Bose exchange effect
余永乐
武汉物理与数学研究所

2. P. Kapitza
Superfluidity in liquid He-4, 1938.
D. D. Osheroff, R. C. Richardson, D. M. Lee
Superfluidity in liquid He-3, 1972.
E. Kim and M. H.W. Chan
Superfluidity in Solid He-4, 2004.

3. Microscopic mechanism of Superfluidity :
F. London, related Superfluidity with BEC, 1938
* O. Penrose, L. Onsager. C. N. Yang, off-diagonal long-range order
* N. N. Bogoliubov’s theory

5. N=10 g=1

6. A metastable state at L=N,
It carries a persistent current.
N=10 g=1

7. A metastable state at L=N, It carries a persistent current.
(Leggett, Rev. Mod. Phys. 73,(2001)
See also, F. Bloch, Phys. Rev. A,7
(1973))
N=10 g=1

8. A metastable state at L=N, It carries a persistent current.
(Leggett, Rev. Mod. Phys. 73,(2001)
See also, F. Bloch, Phys. Rev. A,7
(1973))
Rotating frame
with
N=10 g=1

9. See also: F. Bloch, Phys. Rev. A, 7,2187(1973)
G. M. Kavoulakis, et al. cond-mat/

14. Exact diagonalization:

15. Exact diagonalization:

16. Exact diagonalization:

17. Exact diagonalization:

21. Small g, perturbation

22. Small g, perturbation

23. Small g, perturbation

24. Small g, perturbation

25. Small g, perturbation

26. Small g, perturbation

27. Small g, perturbation

32. Spinor system, each particle has two internal states,

33. Spinor system, perturbation again,

34. Spinor system, perturbation again,

35. Spinor system, perturbation again,
New

36. Spinor system, perturbation again,

37. Spinor system, perturbation again,

41. D C B A

44. Translation
Along x by

45. Translation
Along x by

46. Translation
Along x by

47. Translation
Along x by

53. Linear Dispersion

54. Second Minimum
(Roton)
Linear Dispersion

57. Superfluidity and supersolidity is a Bose exchange
effect. This theory of this complex many-body phenomenon is simple, natural, straightforward, and crystal-clear. It is a victory of quantum mechanics!
Once the quantum nature of superfluidity is revealed, The related important physical issues, such as the relationship between superfluidity and BEC, the origin of rotons, are resolved in a simple and natural way.