Thermal transport manipulated by vortex domain walls in bulk h-ErMnO₃

Topological defects such as structural vortex domain walls (DWs), which induce many intriguing properties and associated physical phenomena in multiferroics, also provide a platform for manipulating thermal transport. Here, we employ time-domain thermoreflectance (TDTR) to study the thermal conductivity of bulk h-ErMnO₃ single crystals with different vortex DWs over a wide temperature range. We find that the vortex DWs can effectively and synergistically suppress the thermal conductivity along (κ_c) and perpendicular (κ_ab) to the c-axis of h-ErMnO₃ single crystals. A phonon scattering model is utilized to explain the mechanism of thermal transport manipulated by vortex DWs. This model yields the intrinsic thermal conductivity and the effective phonon mean free path (MFP) of h-ErMnO₃. The model also manifests that vortex DWs achieve a maximum reduction of ∼28% for the room-temperature thermal conductivity against the single-domain case. The reduction becomes more significant with decreasing temperature due to the longer effective MFP at lower temperatures, both proved experimentally by the cryogenic experiment and theoretically based on the proposed phonon scattering model. These findings not only provide an essential understanding of heat transport in multiferroics with vortex DWs but also pave the way for their application in next-generation ferroelectric devices.