¹⁷O NMR studies of Sr₂RuO₄ with applied uniaxial stresses beyond the Lifshitz transition

Experiments on uniaxially stressed Sr₂RuO₄ have resulted in substantial physical properties changes, including a factor 2.5 increase in the superconducting T_c, and an apparent breakdown of Fermi Liquid behavior in the normal state. Both are attributed to to a strain-induced passing of the Fermi energy through a van Hove singularity (vHs) [1]. Recent μSR measurements gave evidence for a magnetic phase transition at even greater stress [2]. Presented here are the results of ¹⁷O NMR spectroscopy and relaxation measurements. Enhanced relaxation rates characterize a phase boundary consistent with the proposed line of transitions. Nevertheless, within the low-symmetry phase, the NMR spectra are not broadened and (1/T₁T) follows standard Fermi liquid behavior. We discuss the implications of these results, how they relate to the possible type of magnetic order, and the relationship of the reported magnetic order to the superconducting state.

[1] Steppke, A. et al. Science 355, eaaf9398 (2017).

[2] Grinenko, V., Ghosh, S., Sarkar, R. et al. Nat. Phys. 17, 748–754 (2021).