Unlocked polarity and chirality at domain walls of the polar chiral crystal Ni₃TeO₆

It has been of central interest of multiferroic research to explore the nature of coupled order parameters of their domain states. On the other hand, domain walls, the boundaries between different neighboring domains, can be of unique interest, as they may host properties distinct from the domains. Yet, the research attention on domain walls is much less than that on domains. Ni₃TeO₆, a promising multiferroic candidate, hosts an interesting interlock relationship between polarity and chirality. In this presentation, we will report our results obtained by the Second Harmonic Generation (SHG) microscopy that show a ten-fold enhancement of the SHG response at domain walls relative to the signal from the domains. Further, Transmitted Circular Birefringence (TCB) microscopy reveals zero TCB signal at the domain wall. The enhanced SHG signal and the suppressed TCB signal suggests the decoupling between polarity and chirality at the domain walls. We will further discuss our understanding of these measurements in terms of distinct behaviors observed at domain walls.