Suppressing the Decoherence of Alkali-Metal Spins at Low Magnetic Fields

Interactions of electron spins with rotational degrees of freedom during collisions or with external fields are fundamental processes that limit the coherence time of spin gases. We experimentally study the decoherence of hot cesium spins dominated by spin rotation interaction during binary collisions with N2 molecules or by absorption of near-resonant light. We report an order of magnitude suppression of the spin decoherence rate by either of those processes at low magnetic fields. This work extends the use of magnetic fields as a control knob, not only to suppress decoherence from random spin-conserving processes in the spin-exchange relaxation free (SERF) regime but also to suppress processes that relax electron spins rather than conserve them.