Fig. 2

Harmonic signals under different magnetic ordering and laser amplitudes. a HHG signal from a nonmagnetic Fe monolayer. The laser E-field is along the y axis, with ħω = 2.0 eV, τ = 60 fs and field amplitude E₀ = 0.09V/Å, for the results in this figure. The top curve is obtained without using the window function, while the bottom is processed with the window function. b HHG from the spin-up channel in a magnetic Fe monolayer. The spin–orbit coupling is not included. c Similar to b, but from the spin-down channel. d HHG signal with spin-polarized electrons and spin–orbit coupling. The solid and dashed lines denote the signals along the x and y axes, respectively. The spin is orientated perpendicular to the Fe(110) surface. Inset: Phase diagram of P_x(t) versus P_y(t). e Same as d but with E₀ = 0.15V/Å, where high harmonics up to 19th order are observed