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Non-reciprocal transport in non-centrosymmetric materials has attracted immense interest and holds promising prospects for future applications [1]. The physics of non-reciprocal responses delves into crucial elements of modern condensed matter, such as symmetry and quantum geometry. In this talk, we present our findings on non-reciprocal response in the polar bilayer ruthenate Ca₃Ru₂O₇. This material has been extensively studied due to its strong electronic correlations and spin-orbit coupling. This material exhibits antiferromagnetic ordering with moments along the a-axis below T_N = 56K, followed by a spin reorientation transition at T_S = 48K, where the moments flip to the b-axis [2]. Coincidentally, the spin reorientation transition is coupled with an electronic transition where a pseudogap opens and Dirac nodes appear at the M point [3]. In our transport measurements, we found that at temperatures below T_S, nonreciprocal transport behavior is present when the applied current and magnetic field were perpendicular to each other and orthogonal to the polar axis, with the nonreciprocal resistance linearly dependent on the magnetic field.  This study not only marks the first observation of nonreciprocal transport in an oxide material, but also advances our understanding of the interplay between topology and magnetism.

 

 

References:

1. 1. Tokura, Y. & Nagaosa, N. Nonreciprocal responses from non-centrosymmetric quantum materials. Nat Commun 9, 1–14 (2018).
   
   2. Faure, Q. et al. Magnetic structure and field dependence of the cycloid phase mediating the spin reorientation transition in Ca₃Ru₂O₇. Phys. Rev. Res. 5, 013040 (2023).
   
   3. Horio, M. et al. Electronic reconstruction forming a C2-symmetric Dirac semimetal in Ca₃Ru₂O₇. npj Quantum Mater. 6, 1–7 (2021).