Proximity effect of emergent field from spin ice in epitaxial pyrochlore heterostructures*

Geometrically frustrated magnets with macroscopically degenerate ground states are known as quantum magnets, exhibiting exotic spin structures and field-induced emergent quantum phenomena. However, many quantum magnets are insulating in nature, making it challenging to integrate them into electronic devices based on conducting charge carriers. Therefore, there is a growing demand to develop new methods for electrically detecting emergent fluctuations and excitations in quantum magnets without disrupting the spin states.

In this study, we overcome this major challenge by pioneering a new ground of “interfacial emergent magneto-transport phenomena” at a coherent Bi₂Rh₂O₇/Dy₂Ti₂O₇ pyrochlore oxide heterointerface, where Bi₂Rh₂O₇ is a non-magnetic metal and Dy₂Ti₂O₇ is a prototypical spin ice insulator. We spot the fact that quantum magnets are often concomitant with non-coplanar spin textures and serve as a viable platform for an “emergent field” driven by their scalar spin chirality. We observe the angle dependent magnetoresistance that reflects the magnetic phase transition of Dy₂Ti₂O₇. We also detect the topological Hall resistivity as a firm evidence for the sign inversion of the “emergent field” triggered by the spin flop transition of Dy₂Ti₂O₇. This observation particularly demonstrate that the magnetic proximity effect not only induces the conventional anomalous Hall effect proportional to magnetization but also promotes the topological Hall effect through the “penetration” of the emergent field.

Our findings based on coherent heterostructures will bridge the gap between conventional fundamental researches on insulating quantum magnets and their potential electronic applications, possibly leading to a transformative innovation in quantum technologies.