Nonlinear Hall effect in RuO2/TiO2(110)

Uddipta Kar^1*, Wazid Ahmed¹, Fu-En Cheng¹, Akhilesh Kumar Singh¹, Elisha Cho-Hao Lu¹, Javed Iqbal¹, Wei-Chuan Chen¹, Wei-Li Lee¹

¹Institute of Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Uddipta Kar, email:uddiptakar2024@gmail.com

Ruthenium dioxide (RuO2) has recently attracted numerous research interests due to the possibility of hosting a novel altermagnetic phase, which holds promise for future spintronic applications. Despite this excitement, the precise nature of RuO2’s magnetic ordering and symmetry remains under active debate. In recent developments, quantum nonlinearity has emerged as a powerful tool to probe the underlying symmetries in a quantum material [1]. Specifically, theoretical studies indicate that in RuO2, the leading contribution to the third harmonic response arises from the Berry curvature quadrupole, offering a sensitive handle to explore its elusive magnetic phase [2].
In this study, we present temperature-dependent measurements of nonlinear Hall effect (NLHE) in a 8 nm-thick RuO2 film grown on TiO2 (110) substrates patterned into a sunbeam-shaped device, which allows us to investigate magneto-transport anisotropic effects. Intriguingly, We observed vanishing second-order NLHE but pronounced third-order NLHE in RuO2/TiO2 (110), and the magnitude of third-order NLHE appears to be largely enhanced by electron correlation effect below 20 K. In the high temperature regime, detailed scaling of third-order NLHE signals with respect to the Drude electron lifetime will be performed and presented to address the relevant symmetries in RuO2 thin film system [3].

**We acknowledge financial support from the National Science and Technology Council (NSTC Grants No. 108-2628-M-001-007-MY3, No. 110-2112-M-002-030-MY3, and No. 111-2112-M-001-056-MY3).
References:
[1] Sodemann et al., Phys. Rev. Lett. 115, 216806 (2015).
[2] Y Fang et al., Phys. Rev. Lett. 133, 106701 (2024).
[3] Debottam Mandal et al., Phys. Rev. B 110, 195131 (2024).

Keywords: Altermagnetism, NonLinear Hall effect, RuO2