Non-Fermi liquid state and field-induced topological Hall effect in pyrochlore-type Eu₂Mo₂O₇

Topological quantum properties which emerge from the coupling of conduction electrons with complex magnetic structures have attracted much interest. For example, when a conduction electron couples to a non-collinear localized spin, the electronic wavefunction acquires a Berry phase proportional to the scalar spin chirality (SSC). This Berry phase acts as a giant virtual magnetic field and causes the unconventional Hall effect (topological Hall effect). In previous studies, materials which have non-coplanar magnetic structures have been targeted. Recently, the topological Hall effect due to the thermal spin fluctuations has been reported, attracting much attention [1].

We synthesized pyrochlore-type Eu₂Mo₂O₇, the collinear ferromagnetic metal. In this system, we can modify the magnetic interaction from ferromagnetic to antiferromagnetic by applying the pressure. The system shows no magnetic transition above 7 GPa and the resistivity becomes temperature independent. The Hall effect shows a maximum value near the ferromagnetic transition temperature and quantum critical point. These results suggest that the thermal or quantum fluctuation induces SSC and SSC oriented by the magnetic field causes large topological Hall effect.



[1] K. K. Kolincio, et al., PNAS 118, e2023588118 (2021).