Fig. 3.

Emission frequencies and vortex lattice configurations at matching fields. a I–V curves in the vortex velocity versus normalized current representation. The horizontal arrows indicate the vortex velocities at which the emission spectra in Fig. 2 have been acquired. Inset: The I–V curve of the sample at 3 K and 4.2 T. The vertical arrow indicates the definition of I^* used for plotting the I–V curves in the main panel. b Peak frequencies versus vortex velocity for the data sets (c, d) of Fig. 2. c Resistance as a function of H^||b for a series of temperatures, as indicated. The vortex lattice configurations, which commensurate with the Mo/Si superlattice at $H_{N=2}^{\left(2\right)}=3.15$ T and $H_{N=1}^{\left(1\right)}=4.2$ T, are shown in the scaled coordinate system (γa, c) in the inset. d Normalized emission power P_m as a function of temperature for the first four lowest-order harmonics $f_0^{\left(2\right)}=10.02$ GHz emitted at the vortex velocity v = 100 m s⁻¹ at 3.15 T. Solid lines are guides for the eye