  Antiferromagnets have attracted extensive interest as platforms for nanoscale
spintronic devices owing to ultrafast spin dynamics and lack of a stray field.
One of the crucial missing pieces in antiferromagnets is a quantum-mechanical
electric field known as an emergent electric field, which has been observed for
the motion of ferromagnetic spin texture. Since this phenomenon allows for the
development of novel spintronic devices such as quantum inductors, its
identification in antiferromagnets is vital for developing nanoscale spintronic
devices. Here, we demonstrate that the motion of antiferromagnetic spin
textures generates an emergent electric field. In a room-temperature
antiferromagnet FeSn2, we observed large current-nonlinear responses in the
imaginary part of the complex impedance at and well above room temperature.
This signal is attributed to an emergent electric field resulting from the
nonadiabatic electron spin dynamics during the current-induced motion of
antiferromagnetic domain walls. Notably, the observed electric response is
strongly enhanced as the sample size decreases and robust against magnetic
fields. Our finding may pave the way for novel nanoscale quantum spintronic
devices.
