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J. Pei (UTK/ORNL) With: W. Nazarewicz, J. Dukelsky

DFT Study of Exotic Pairing Phases in Imbalanced Fermi Condensates. J. Pei (UTK/ORNL) With: W. Nazarewicz, J. Dukelsky. Expected exotic FFLO pairing. In imbalanced Fermi systems, pairing with none-zero momentum can happen: Flude-Ferrell-Larkin-Ovchinnikov ( FFLO )

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J. Pei (UTK/ORNL) With: W. Nazarewicz, J. Dukelsky

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  1. DFT Study of Exotic Pairing Phases in Imbalanced Fermi Condensates J. Pei (UTK/ORNL) With: W. Nazarewicz, J. Dukelsky

  2. Expected exotic FFLO pairing • In imbalanced Fermi systems, pairing with none-zero momentum can happen: Flude-Ferrell-Larkin-Ovchinnikov (FFLO) Oscillation pairing gap is expected; Modulated densities (crystallized). • It exists in many theoretical calculations, but difficult to find. • Some signatures in heavy fermions systems. Radovan, et al. Nature 425, 51, 2003.

  3. Some experiments • Advantages of using cold atoms: interaction is controllable; clear physics; High Tc; implications for other Fermi systems • Unitary limit: two body s-wave scattering length diverges: as→±∞ System is strongly correlated and its properties do not dependent on the value of scattering length as • Trapped by optical and magnetic potential approximate HO potential: Aspect ratio:η=wr/wz 834 G highly elongate trap is of great interests! (good for looking FFLO pairing)

  4. Experiments(Rice) • Phase Separation • Superfluid Core is deformed from the trap shape and such deformation effects disappear at high temperatures • Trap aspect ratio～50: highly elongate • Particle numbers～105 G.B.Partridge, et al, PRL97,190407,2006 G.B.Partridge, et al, Science,311,503,2006

  5. Experiments(MIT) • Phase separation • However, no superfluid core deformation Y.Shin, et al, PRL 97,03401,2006 • Clogston-Chandrasekhar limit of superfluidity • Trap aspect ratio=5, particles=106

  6. Experiments-others • French group: 105 particles, aspect ratio=23 (agree with MIT) No core deformation • Question??? • different experimental conditions • or theory is not precise C. Salomon, et al, PRL103, 18 (2009) 170402

  7. Finite-size effect • Finite-size effect of trap deformations and particle numbers small deformation trap doesn't violate LDA solutions • Surface tension is important at large deformations M.Ku, PRL 102, 255301, 2009 Sensarma, et al. arxiv: 07061741 Tezuka, et al. arxiv: 0811.1650 • Non-equilibrium state observed in Rice experiment Parish, et al. PRA 063305(2009) T.N. De Silva, et al, PRL 97, 070402(2006)

  8. normal FFLO PS BP TK Koponen,PRL 99,120403 Theoretics • Quantum Monte Carlo: QMC is very precise but limited to small systems • Bogoliubov de-Genes equation: Mean Field approximation Plenty of calculations, no Hartree potential, and not quantitatively accurate A contest of computation: Tokyo U:30000 particles; Rice U: 105 particles • DFT: at the unitary limit, the physical properties only depends on the density. It is good for DFT descriptions. Superfluid Local Density Approximation (SLDA) is very precise.

  9. Coexistence of difference phase? • SDLA calculations with different initials sin(qz)exp(-(z-zc)/a), why sensitive? Quasi-continuum back ground J.P, W. Nazarewicz, J. Dukelsky, arxiv:1005:3239

  10. discussions Is that Quantum fluctuations can be considered by a generator-coordinate DFT FFLO is a superposition of different wavepackets

  11. SLDA and ASLDA difference • Very different Hartree potentials in ASLDA • Related to different effective mass Deformed core solution is washed out in ASLDA. Because of their different Hartree potentials BdG calculations are similar to SLDA calculations.

  12. Propose to access LO states • Pairing oscillations become remarkable as trap aspect ratio increase • The oscillations are perpendicular to the long axis • Oscillation periods are almost the same. Periods are related to the qLO Numerical: evolve the trap from a ground-state solution at a moderately elongated trap to reach an excited state Experiments: can be accessible by elongate the trap adiabatically.

  13. Conclusions • Phase separation is demonstrated in trapped system both by SLDA and ASLDA • Energy structures of coexistent phases are shown. • Superfluid Core deformation is not shown in ASLDA. • The FFLO is predicted in highly elongated trap, both by SLDA and ASLDA. However, It has a higher energy than LDA solution. Could be access by experiments, need very low temperature. Thanks: A. Bulgac, M.M. Forbes

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