Enhanced detectability of axion's electromagnetic response with a RF-excited magnetic field in cavity

Abstract

Haloscope is one of the typical installations to detect the electromagnetic responses (EMRs) of axion field in radio-frequency (RF) and microwave bands. Given that the detectable signals of the usual Haloscope-type detectors (HTDs), biased only by high stationary magnetic fields, are just the second axion-photon energy and thus are very weak, here we propose a feasible approach to significantly improve their sensitivity by additionally applying a transverse RF- or microwave modulated magnetic field to excite the cavity's magnetic resonant mode to produce the first-order axion-photon energy response signals. Accordingly, it can be argued that the achievable detection sensitivity of the upgrading HTD (i.e., UHTD) could be enhanced by $3\sim 4$ orders of magnitude, compared with that achieved by the existing HTDs without the transverse RF-excited magnetic field. The feasibility of the proposed UHTD is also discussed.