Self-generated Floquet modulation in a multiharmonic-dressed alignment-based magnetic-resonance system

Quantum systems with multiharmonic dressing have been extensively investigated and exhibited various novel phenomena and technologies by virtue of their robust electromagnetic response. Here we mainly investigate the self-generated longitudinal Floquet modulation phenomenon of an alignment-based magnetic-resonance system with pump-probe structure dressed by two different transverse radio-frequency (rf) fields in a warm atomic cesium ensemble, both theoretically and experimentally. The self-generated Floquet modulation includes first and second harmonics, which are contributed to by linear and nonlinear processes from the weak-dressed field, respectively. The self-generated Floquet modulation dresses the alignment absorption spectra into two continua. The asymmetry of each dressed continuum is due to the generalized parity symmetry of the system being broken by the second harmonic modulation. Moreover, the nonlinear modification effect of the weak rf field on the probe verifies the existence of the four-wave mixing process in the rf band. The analytical expression, establishment process, and asymmetry analysis of the continua are given concisely. Our results can be applied to the fields of precision magnetic-field measurement, quantum control, quantum simulation, and so on. In addition, because the physical mechanism is universal, it can be applied not only to an atomic ensemble, but also to solid-state devices.