Fig. 5: Reflectance change in the MnTe film induced by laser irradiation.

a Reflectance change behavior in the MnTe film, induced by laser irradiation, as a function of pump laser power. V/V₀ corresponds to the normalized reflectance detected by a photodiode. First, the α-MnTe film was irradiated with the pump pulse laser at the same position and its power was gradually increased. After the reflectance dropped, the laser power returned to zero and then again gradually increased, irradiating at the same position than the first measurement. b Cross-sectional transmission electron microscopy (TEM) image of the MnTe film that showed a reflectance decrease by laser irradiation. Scale bar: 100 nm. Schematic of the cross-section of the MnTe film is shown in right inset. Only a small part near surface is supposed to be active region. c Selected area diffraction patterns (SADPs) and inverse fast Fourier transform (IFFT) images of high-resolution TEM (HR-TEM) images taken from α-matrix enclosed by the red-dotted line (left) and active region enclosed by the blue-dotted line (right). Scale bar: 5 Å. The active region exhibits a β′-phase. In the IFFT images, both Mn and Te atoms were observed in the β′-phase, whereas only Mn atoms were visible in the α-phase. Both images were well fitted with the simulation results at a film thickness of t = 9.9 nm and defocus \(\Delta f\) = +2 (see Supplementary Fig. 8a, b).