Interfacial Asymmetry and Surface Roughness Enhanced Topological-Hall-Like Transport in SRO/BTO/SRO Trilayers

Engineering heterostructure architecture in complex oxides offers a promising route for tuning emergent topological transport. Here, we show that replacing a single-interface BaTiO₃/SrRuO₃ (BTO/SRO) bilayer with an SRO/BTO/SRO trilayer produces a pronounced enhancement of the topological-Hall-like response. The trilayer exhibits a maximum extracted topological-Hall-like resistivity of 0.8 µΩ cm, approximately 2.5 times larger than that of the bilayer, together with a broad stability window from 5 to 90 K. Atomic-scale strain and polarization/displacement mapping reveal structurally and electrostatically nonequivalent upper and lower SRO environments, while AFM shows substantially greater morphological modulation in the trilayer. Micromagnetic simulations demonstrate that noncoplanar magnetic configurations are physically permissible over a finite parameter range in this architecture. However, because the two nonequivalent SRO layers may also contribute distinct anomalous Hall channels, the microscopic origin of the hump-like Hall contribution cannot be uniquely assigned from the present transport measurements. The experimentally established result is that the trilayer architecture substantially enhances and broadens the topological-Hall-like response compared with the bilayer.