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arXiv · 2003.13340

Theory of Strain-Induced Magnetic Order and Splitting of $T_c$ and $T_{\rm TRSB}$ in Sr$_2$RuO$_4$

Astrid T. Rømer·Andreas Kreisel·Marvin A. Müller·P. J. Hirschfeld·Ilya M. Eremin·Brian M. Andersen
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Abstract

The internal structure of the superconducting state in Sr$_2$RuO$_4$ remains elusive at present, and exhibits evidence for time-reversal symmetry breaking. Recent muon spin relaxation measurements under uniaxial strain have revealed an increasing splitting between the superconducting critical temperature $T_c$ and the onset of time-reversal symmetry breaking $T_{\rm TRSB}$ with applied strain [Grinenko et al., arXiv:2001.08152]. In addition, static magnetic order is induced by the uniaxial strain beyond $\sim$1 GPa, indicating that unstrained Sr$_2$RuO$_4$ is close to a magnetic quantum critical point. Here, we perform a theoretical study of the magnetic susceptibility and the associated pairing structure as a function of uniaxial strain. It is found that the recent muon relaxation data can be qualitatively explained from the perspective of spin-fluctuation mediated pairing and the associated strain-dependence of accidentally degenerate pair states in unstrained Sr$_2$RuO$_4$. In addition, while unstrained Sr$_2$RuO$_4$ features mainly $(2\pi/3,2\pi/3)$ magnetic fluctuations, uniaxial strain promotes $(\pi,\pm\pi/2)$ magnetism.

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Astrid T. Rømer, Andreas Kreisel, Marvin A. Müller, P. J. Hirschfeld, Ilya M. Eremin, Brian M. Andersen. 2020-03-30. Theory of Strain-Induced Magnetic Order and Splitting of $T_c$ and $T_{\rm TRSB}$ in Sr$_2$RuO$_4$. https://doi.org/10.1103/physrevb.102.054506

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