A proof-of-principle experiment of EIT with gamma radiation in FePSe₃ single crystal

Synthesis of FePSe₃ single crystal was attempted, and Electromagnetically Induced Transparency (EIT) was investigated using the synthesized crystal as the absorber. By lowering the temperature and increasing the magnetic splitting of ⁵⁷Fe Moessbauer nuclei, the energy levels of m_e=-3/2 and m_e=+1/2 cross at one point, and the two peaks overlap. In this overlapping condition, γ-ray becomes coherent, and quantum interference occurs. This seemed to result in EIT. Utilizing this phenomenon, EIT was investigated experimentally. Also, in order to investigate the effect of EIT when the axis of magnetic field is tilted against the crystal axis, experiment with external magnetic field was also conducted. When the fitting parameters for Moessbauer spectrum analysis were fixed at theoretical values calculated based on least square method, a decrease in absorption was observed between 14.5 and 71 K. It was assumed that quantum energy level mixing resulted in this range in the temperature of absorption decrease. In addition, the analysis based on the assumption that one peak splits due to defective absorption by EIT resulted in the best agreement with the results in term of the conditions when EIT occurs. (S.K.)