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Multi-component quantum gases show very rich dynamics as they offer possibilities for an exchange of population between different quantum gas components - a favourable system in this respect are quantum gases with spin degree of freedom.
We will discuss the magnetic properties of these spinor quantum gases as well as novel effects in the interaction of condensate fractions and normal components. In particular we study the dynamic evolution and magnetic ground states in spinor Bose-Einstein condensates of 87Rb [1]. We present the magnetic phase diagrams in comparison to the experimental properties of 87Rb Bose-Einstein condensates in the F=1 and F=2 hyperfine states, which we interestingly find to behave ferromagnetic in the F=1 state but antiferromagnetic in the F=2 state. For further coupling and manipulation schemes of these magnetic phases a low magnetic field mixed-spin-channel Feshbach resonance that we have studied might be well suited [2]. As a main point we investigate different thermalisation regimes in multi component spinor systems, which allow novel studies on 'condensate melting’ [3] and even allow a 'new’ realisation of BEC which does not rely on cooling down an ensemble of atoms but adding more and more particles at constant temperature to the system [4]. [1] H. Schmaljohann, M. Erhard, J. Kronjäger, M. Kottke, J.J. Arlt, K. Bongs and K. Sengstock; 'Dynamics of F=2 Spinor Bose-Einstein Condensates', Phys. Rev. Lett. 92, 040402 (2004). [2] M. Erhard, H. Schmaljohann, J. Kronjäger, K. Bongs and K. Sengstock; 'Measurement of a Mixed-spin-channel Feshbach Resonance in 87Rb', Phys. Rev. A 69, 032705 (2004). [3] M. Erhard, H. Schmaljohann, J. Kronjäger, K. Bongs, K. Sengstock; ’Dynamics and Thermodynamics in Spinor Quantum Gases’, Appl. Phys. B, invited, in press (2004). [4] M. Erhard, H. Schmaljohann, J. Kronjäger, K. Bongs, K. Sengstock; ’Bose-Einstein Condensation at Constant Temperature’, Phys. Rev. A 70, R031602 (2004). |