Pairing symmetry and nonreciprocal Josephson effect in Sr₂RuO₄ and UTe₂
ORAL
Abstract
Sr₂RuO₄ and UTe₂ are candidates for odd-parity, spin-triplet pairing with their symmetry properties of the orbital and spin parts of the superconducting order parameter (OP) locked due to the presence of inversion symmetry. In addition, the time-reversal symmetry (TRS) has been shown to be broken in Sr₂RuO₄ by multiple muon spin rotation measurements carried out over the years (1). The phase-sensitive measurements probing the orbital part of OP rely on the Josephson coupling of an s-wave superconductor and Sr₂RuO₄ (2) However, nonreciprocal Josephson effect is not guaranteed by the TRS breaking in the bulk of Sr₂RuO₄. We observed clear nonreciprocal behavior in the Josephson coupling between Sr₂RuO₄ and In0.5Au0.5 but not in Josephson junctions of Sr₂RuO₄/TiAl, neither did we in UTe2/In Josephson junctions. We will also present data obtained from corner junctions of Sr₂RuO₄/In0.5Au0.5, showing that the pairing symmetry in Sr₂RuO₄ is p-wave (and therefore, spin-triplet) and discuss the current controversy on the pairing symmetry in this superconductor (3).
*Work on UTe2 was carried out in collaboration with Camilla M. Moir, Eric Lee-Wong, Ryan E. Baumbach and M. Brain Maple.Research at Penn State was supported by the National Science Foundation (NSF) under Grant No. DMR-2312899.Crystal growth was further supported by the Penn State 2D Crystal Consortium–Materials Innovation Platform (2DCC-MIP) under NSF Cooperative Agreement DMR-2039351.
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Publication:1. For the most recent work, see R. Khasanov, A. Ramires, V. Grinenko, I. Shipulin, N. Kikugawa, D. A. Sokolov, J. A. Krieger, T. J. Hicken, Y. Maeno, H. Luetkens, and Z. Guguchia, "In-plane magnetic penetration depth in Sr2RuO4: Muon-spin rotation and relaxation study." Phys. Rev. Lett. 131, 236001 (2023). 2. K. Nelson, Z-Q. Mao, Y. Maeno, and Y. Liu, "Odd-parity Superconductivity in Sr2RuO4", Science 306, 1151 (2004) 3. Anthony J. Leggett and Ying Liu, "Symmetry properties of superconducting order parameter in Sr2RuO4," Journal of Superconductivity and Novel Magnetism, 34, 1647–1673 (2021). (A Festschrift in honor of Brian Josephson, 2020.)
