冷原子试验之基本原理(I).PPT

冷原子實驗之基本原理(I) 韓殿君 國立中正大學物理系 2003年 8月5日 於理論中心 Outline Introduction Works on the Degenerate Bose Gas Cooling, Trapping, and Manipulating Tools BEC Behavior Remarks on the Current BEC Experiments and Future Directions Introduction Brief History of Bose-Einstein condensation (BEC) Special Features of Dilute Bose condensates (Why dilute is important?) Goal to achieve? Momentum space p: Cooling: lower T → larger ?d Coordinate(Position) space r: Trapping: increase n → smaller d Works on the Degenerate Bose Gas Cooling, Trapping, and Manipulating Tools Tools: Electric and magnetic fields (DC and AC ) EM waves – photons (visible, IR, microwave …) Systems: Atomic ensembles (atom number: 103 – 109) Macroscopic size: 5 – 500 ?m Ultrahigh vacuum environment (very little impurities) Ultralow temperatures (? 1 ?K) No physical wall Quiet and almost no defect potentials (as in the texbooks) are possible Magnetic Trapsnot all the states are Trappable!! Optical Dipole Trap BEC Behavior Starting from the Gross-Pitaevskii equation!! Time-Evolution of a Wavefunction in Free Space Thomas-Fermi Regime NBEC 105 atoms ? Thomas-Fermi regime kinetic energy internal energy Cloud shape ? inverted paraboloid Phase transition (Lambda Point) Remarks on the Current BEC Experiments and Future Directions Collective Mode Excitations Sound Propagation Superfluidity and Vortices Skyrmions in a Multicomponent BEC - point-like excitation Utrecht, 2001 Two-Component Condensates Spinor Condensates Coherence and Correlation Superradiant Rayleigh Scattering Matter Wave Amplification Nonlinear Atom Optics - Four Wave Mixing Bright Solitons Fechbach Resonaces- a tuning tool for atom-atom interaction Optical Lattices Quantum Phase Transition 超流態轉變為非超流態(Mott 絕緣態)之量子相變 Max-Planck Institute,