Microscopic Ginzburg-Landau theory and singlet ordering in Sr2RuO4

Wagner, Glenn, Røising, Henrik S., Flicker, Felix ORCID: https://orcid.org/0000-0002-8362-1384 and Simon, Steven H. 2021. Microscopic Ginzburg-Landau theory and singlet ordering in Sr2RuO4. Physical Review B 104 (13) , 134506. 10.1103/PhysRevB.104.134506

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Abstract

The long-standing quest to determine the superconducting order of Sr 2 RuO 4 (SRO) has received renewed attention after recent nuclear magnetic resonance (NMR) Knight shift experiments have cast doubt on the possibility of spin-triplet pairing in the superconducting state. As a putative solution, encompassing a body of experiments conducted over the years, a ( d + i g ) -wave order parameter caused by an accidental near degeneracy has been suggested [S. A. Kivelson et al., npj Quantum Mater. 5, 43 (2020)]. Here we develop a general Ginzburg–Landau theory for multiband superconductors. We apply the theory to SRO and predict the relative size of the order parameter components. The heat capacity jump expected at the onset of the second-order parameter component is found to be above the current threshold deduced by the experimental absence of a second jump. Our results tightly restrict theories of d + i g order, and other candidates caused by a near degeneracy, in SRO. We discuss possible solutions to the problem.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Physics and Astronomy
Publisher:	American Physical Society
ISSN:	2469-9950
Date of First Compliant Deposit:	6 January 2023
Date of Acceptance:	28 September 2021
Last Modified:	07 Jan 2024 17:10
URI:	https://orca.cardiff.ac.uk/id/eprint/155511

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