Fig. 5
From: Nonreciprocal responses from non-centrosymmetric quantum materials
Second-harmonic (SH) generation from the toroidal moments in multiferroics. a Crystal and magnetic structures of GaFeO3. In the right panel, outward (inward) arrows represent the spin direction of Fe1 (Fe2) atoms antiparallel (parallel) to the c axis. Horizontal solid lines represent the shifted positions of Fe ions along the b axis from the symmetric positions (dashed lines) of FeO6 octahedra. Note that the shifted directions of Fe1 and Fe2 atoms are opposite to each other. Reprinted figure with permission from ref60. Copyright (2005) by the Physical Society of Japan. b Experimental configuration for the measurement of the Kerr rotation of SH light in a GaFeO3 crystal (left panel). Analyzer-angle dependence of SH intensity at 180 K (<TC). Analyzer angles θ of 0 and 90° stand for p- and s-polarized SH light, respectively. Solid and open circles indicate the SH intensity for +z and –z directions of the magnetic field, respectively. c (Left) topographic image of the ac surface of the GaFeO3 crystal as taken by the SH light in the nonmagnetic configuration, i.e., Pin-Pout. Magnetic domains aligned along the c axis were observed by reflected SH intensity in (center) Sin(S + P)out and (right) Sin(S–P)out configurations. Reprinted figure with permission from ref59. Copyright (2004) by the American Physical Society
