  We show scalable and complete suppression of the recently reported
terahertz-pulse-induced switching between different resistance states of
antiferromagnetic CuMnAs thin films by ultrafast gating. The gating
functionality is achieved by an optically generated transiently conductive
parallel channel in the semiconducting substrate underneath the metallic layer.
The photocarrier lifetime determines the time scale of the suppression. As we
do not observe a direct impact of the optical pulse on the state of CuMnAs, all
observed effects are primarily mediated by the substrate. The sample region of
suppressed resistance switching is given by the optical spot size, thereby
making our scheme potentially applicable for transient low-power masking of
structured areas with feature sizes of ~100 nm and even smaller.
