What influence does a magnetic field have on a Bose-Einstein condensate? Perhaps the answer could include the following possible scenarios:

*

*a static external magnetic field supports the formation of a BEC,

*the magnetic field maintains the BEC longer as the temperature rises,

*a changing magnetic field destroys the BEC,

or other aspects.
 A: It depends on how the magnetic fields are utilised. For example,
Static external magnetic fields can support a BEC as long as the field has a non-zero field minimum such as the Ioffe Pritchard trap or the time-averaged orbiting potential trap (TOP trap). Thermal atoms can be trapped in a quadrupole magnetic field, which has a field zero. However, when using radio-frequency cooling to remove the hottest atoms in a quadrupole field to lower the temperature towards BEC, atoms around the field zero undergo Majorana spin flips and are lost from the trap. The atoms that are lost are the coolest (low energy) atoms, this is then a heating mechanism which prohibits the creation of a BEC in the magnetic trap having a field zero.
Changing magnetic fields can also cause Majorana spin flips, if the rate of change of the field is comparable to the Lamor precession frequency then spin flips will occur, this is how forced rf evaporation works and is a method to cool and create BECs in magnetic traps, but can also be a loss and heating mechanism. Note that this also occurs for atoms moving within a static field as the field is moving from the atoms frame of reference, and is the loss mechanism discussed above.
Combining static and time dependent magnetic fields can be used to create radio-frequency dressed potentials. The static field defines a quantisation axis and splits the degeneracy of the magnetic sub levels, and the time dependent field couples the sub levels. Under the right conditions atoms are trapped in a surface of resonance and the polarisation of the time dependent fields used to modulate the potential within it. BECs have been produced in these traps. The advantage of these traps is that the potential landscape can be dynamically controlled with the phase of the time dependent fields, such that beams splitters and interferometers can be realised for BECs.
