Detection of long-range coherence in driven hot atomic vapors by spin noise spectroscopy

We study intriguing dynamical features of hot Rubidium atoms driven by two light fields. The fields resonantly drive multiple Zeeman states within two hyperfine levels, yielding a cascaded-$\mathrm{\Lambda }$ like structure in the frequency space. A non-Hermitian Floquet tight-binding lattice with imaginary hopping between the nearest states effectively describes the coherence dynamics between Zeeman states within the ground hyperfine manifold. By performing spin noise spectroscopy, we observe higher harmonic peaks in the noise spectrum that capture multi-photon transitions in the ground manifold. Moreover, the peak amplitudes reveal an exponential decay of long-range coherence with increasing separation between the ground states.