1. Aspects of Color Superconductivity in 2-flavor Quark Matter
Lianyi He
Collaborated with Meng Jin, Ying Jiang and Pengfei Zhuang
Physics Department, Tsinghua University
2019/4/8
CSQCD II, KIAA, PKU

2. Outline Chromomagnetic instability and melting pattern
of diquark condensate
Significance of pairing fluctuation and pseudogap in hot quark matter
2019/4/8
CSQCD II, KIAA, PKU

3. Melting pattern of diquark condensate
Chromomagnetic instability
and
Melting pattern of diquark condensate
2019/4/8
CSQCD II, KIAA, PKU

4. Quark Matter Phase Diagram from NJL
weak coupling
strong coupling
S. B. Ruester, et al, PRD72:034004,2005; D.Blaschke et al, Phys.Rev. D72 (2005)
Comments：
1)Self-consistent treatment of quark masses
2)Need to be improved due to chromomagnetic instability
3)The melting pattern NQ-g2SC-NQ ?!
2019/4/8
CSQCD II, KIAA, PKU

5. Chromomagnetic instability
Chromomagnetic instability of CSC in neutral quark matter :
Meissner mass of some gluons become imaginary!
For 2-flavor and zero T,
M.Huang and I.Shovkovy, Phys.Rev. D70 (2004)
Blue line: 8th gluon
Green line: 4,5,6,7th gluon
Similar to the negative superfluid density in asymmetrical
fermion superfluids, new interests due to the appearance
of instability in the gapped phase
2019/4/8
CSQCD II, KIAA, PKU

6. Homogeneous 2SC Solution
NQ-g2SC-NQ
2019/4/8
CSQCD II, KIAA, PKU

7. T-Dependence of Meissner Masses
2019/4/8
CSQCD II, KIAA, PKU

8. LOFF vs Gluonic Phase LOFF Gluonic (simplest version)
Gorbar & Miransky, PLB, 2005
2019/4/8
CSQCD II, KIAA, PKU

9. Similar results for gluonic phase
Neutral LOFF solution
LOFF
1)anisotropic phases enter the low-T domain
2)Restoration of phase coherence at low T
3)Diquark condensate remains a monotonous function of T
Similar results for gluonic phase
O. Kiriyama, arXiv:
2019/4/8
CSQCD II, KIAA, PKU

10. Quark Matter Phase Diagram
LOFF, Gluonic, Mixed phase?
Gluonic phase
Mixed phase impossible
D.Blaschke et al, Phys.Rev. D72 (2005)
2019/4/8
CSQCD II, KIAA, PKU

11. pseudogap in hot quark matter
Significance of pairing fluctuation and
pseudogap in hot quark matter
2019/4/8
CSQCD II, KIAA, PKU

12. BCS-BEC crossover? Interaction strength
So, what is the BCS-BEC crossover? Consider a two-component Fermi gas with attractive interactions. When the interaction is weak, we have the BCS fermionic superfluidity of Cooper-pairs, and we know that these Cooper-pairs are long-range objects. As the interaction increases, the size of Cooper-pairs becomes smaller and smaller, and finally can be regarded as a point-like structure, or molecules. We then can have a condensate of molecules. These two limits, BCS and BEC limits, are actually well-understood, however, the regime between these limits, is not so clear, and is to explored.
To access the crossover, of course, the interaction strength should be enhanced enough large.
BEC of molecules
BCS fermionic superfluidity
Interaction strength
Fermions with two spin states with attractive interactions
2019/4/8
CSQCD II, KIAA, PKU

13. pesudogap bound states
Temperature effects in BCS-BEC crossover
So, what is the BCS-BEC crossover? Consider a two-component Fermi gas with attractive interactions. When the interaction is weak, we have the BCS fermionic superfluidity of Cooper-pairs, and we know that these Cooper-pairs are long-range objects. As the interaction increases, the size of Cooper-pairs becomes smaller and smaller, and finally can be regarded as a point-like structure, or molecules. We then can have a condensate of molecules. These two limits, BCS and BEC limits, are actually well-understood, however, the regime between these limits, is not so clear, and is to explored.
To access the crossover, of course, the interaction strength should be enhanced enough large.
pesudogap bound states
2019/4/8
CSQCD II, KIAA, PKU

14. !!! Color supercondutors at Significance of pairing fluctuation
BCS superconductors
High Tc superconductors
Resonant superfluids with cold atoms
Color supercondutors at
!!!
2019/4/8
CSQCD II, KIAA, PKU

15. Arxiv:
2019/4/8
CSQCD II, KIAA, PKU

16. Self-consistent T-matrix theory
L.P.Kadanoff and P.C.Martin, Phys.Rev. 124, 670(1961)
NSR
Levin group, Phys.Rept.412, 1(2005)
2019/4/8
CSQCD II, KIAA, PKU

17. All colors are gapped at Tc, in contrast to T=0
No diquark bound
states, but pseudogap
still exists
All colors are gapped at Tc, in contrast to T=0
2019/4/8
CSQCD II, KIAA, PKU

18. 2019/4/8
CSQCD II, KIAA, PKU

19. Phase Diagram of High Tc Superconductor
So, what is the BCS-BEC crossover? Consider a two-component Fermi gas with attractive interactions. When the interaction is weak, we have the BCS fermionic superfluidity of Cooper-pairs, and we know that these Cooper-pairs are long-range objects. As the interaction increases, the size of Cooper-pairs becomes smaller and smaller, and finally can be regarded as a point-like structure, or molecules. We then can have a condensate of molecules. These two limits, BCS and BEC limits, are actually well-understood, however, the regime between these limits, is not so clear, and is to explored.
To access the crossover, of course, the interaction strength should be enhanced enough large.
2019/4/8
CSQCD II, KIAA, PKU

20. Thank You!
2019/4/8
CSQCD II, KIAA, PKU