Probing Ultrafast Magnetization Dynamics Via Synthetic Axion Fields Leon Shaposhnikov by Leon Shaposhnikov, 1, * Eduardo Barredo-alamilla, 1, 1school Of Physics And Engineering, Itmo Un2department Of Physics, Stockholm Uni3center For Theoretical Physics, Massachusetts Institute Of4department Of Physics, Arizona State Unizek instant download after payment.

Spatial structuring of materials at subwavelength scales underlies the concept of metamaterialspossessing exotic properties beyond those of the constituent media. Temporal modulation of materialparameters enables further functionalities. Here, we show that high-frequency oscillations of spatiallyuniform magnetization generate an effective dynamic axion field embedding the amplitude and phase ofmagnetization oscillations. This allows one to map ultrafast magnetization dynamics using a probe signalwith much lower frequency.DOI: 10.1103/2rrr-glynIntroduction—The optics of time-varying media [1–4]which has been the focus of much interest in fundamentalhas a long history with pioneering studies dating back to thephysics [25], condensed matter [26–29], and photonics1950s through the 1970s [5,6]. Recent advances in materi[30–34], is an outstanding target in this area.als engineering and nanofabrication have revived interestEmergent axion fields demonstrated previously in conin this field, bringing the realization of time-modulateddensed matter and photonics rely on the spatially varyingphotonic structures within experimentalists’ reach [7–11].magnetization distribution with the zero net magnetizationModulating the material parameters in time unlocks a setcharacteristic to antiferromagnets [Fig. 1(a)]. In turn,of interesting functionalities [12,13]. Since the systemelementary excitations in those structures known as spinvaries in time, energy is generally not conserved [5]. Inwaves or magnons render the effective axion field timeparticular, this enables strong and selective amplificationdependent [35,36].of radiation [14–16], frequency conversion [17], and evenIn this Letter, we put forward a novel mechanism whenradiation from stationary charges [18]. Furthermore, temthe effective axion field arises due to the rapid temporalporal modulation of the medium can break time-reversalmodulation of spatially homogeneous