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Article

Electronic Structure Correspondence of Singlet-Triplet Scale Separation in Strained Sr2RuO4

1
King’s College London, Theory and Simulation of Condensed Matter, The Strand, London WC2R 2LS, UK
2
Institute for Molecules and Materials, Radboud University, NL-6525 AJ Nijmegen, The Netherlands
3
National Renewable Energy Laboratory, Golden, CO 80401, USA
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2021, 11(2), 508; https://doi.org/10.3390/app11020508
Received: 4 November 2020 / Revised: 14 December 2020 / Accepted: 24 December 2020 / Published: 6 January 2021
At a temperature of roughly 1 K, Sr2RuO4 undergoes a transition from a normal Fermi liquid to a superconducting phase. Even while the former is relatively simple and well understood, the superconducting state has not even been understood after 25 years of study. More recently, it has been found that critical temperatures can be enhanced by the application of uniaxial strain, up to a critical strain, after which it falls off. In this work, we take an “instability” approach and seek divergences in susceptibilities. This provides an unbiased way to distinguish tendencies to competing ground states. We show that in the unstrained compound, the singlet and triplet instabilities of the normal Fermi liquid phase are closely spaced. Under uniaxial strain, electrons residing on all orbitals contributing to the Fermiology become more coherent, while the electrons of the Ru-dxy character become heavier, and the electrons of the Ru-dxz,yz characters become lighter. In the process, Im χ(q,ω) increases rapidly around q = (0.3,0.3,0)2π/a and q = (0.5,0.25,0)2π/a, while it gets suppressed at all other commensurate vectors, in particular at q = 0, which is essential for spin-triplet superconductivity. We observe that the magnetic anisotropy under strain drops smoothly, which is concomitant with the increment in singlet instability. Thus, the triplet superconducting instability remains the lagging instability of the system, and the singlet instability enhances under strain, leading to a large energy-scale separation between these competing instabilities. However, since this happens even without spin-orbit coupling, we believe it is primarily the enhancement in the spin fluctuation glue around quasi-anti-ferromagnetic vectors that drives the Cooper pairing instead of the magnetic anisotropy. At large strain, an instability to a spin density wave overtakes the superconducting one. The analysis relies on a high-fidelity, ab initio description of the one-particle properties and two-particle susceptibilities, based on the quasiparticle self-consistent GW approximation augmented by dynamical mean field theory. This approach is described and its high fidelity confirmed by comparing to observed one- and two-particle properties. View Full-Text
Keywords: unconventional superconductivity; spin susceptibilities; vertex functions; triplet superconductivity; hund’s metals; spin density wave; gap symmetry unconventional superconductivity; spin susceptibilities; vertex functions; triplet superconductivity; hund’s metals; spin density wave; gap symmetry
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MDPI and ACS Style

Acharya, S.; Pashov, D.; Chachkarova, E.; Schilfgaarde, M.v.; Weber, C. Electronic Structure Correspondence of Singlet-Triplet Scale Separation in Strained Sr2RuO4. Appl. Sci. 2021, 11, 508. https://doi.org/10.3390/app11020508

AMA Style

Acharya S, Pashov D, Chachkarova E, Schilfgaarde Mv, Weber C. Electronic Structure Correspondence of Singlet-Triplet Scale Separation in Strained Sr2RuO4. Applied Sciences. 2021; 11(2):508. https://doi.org/10.3390/app11020508

Chicago/Turabian Style

Acharya, Swagata, Dimitar Pashov, Elena Chachkarova, Mark v. Schilfgaarde, and Cédric Weber. 2021. "Electronic Structure Correspondence of Singlet-Triplet Scale Separation in Strained Sr2RuO4" Applied Sciences 11, no. 2: 508. https://doi.org/10.3390/app11020508

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