Phenomenological model of the third-harmonic magnetic response due to superconducting fluctuations: Application to Sr2RuO4

Scientific paper - Original scientific paper

• Author: Fei Chen
• Author: Damjan Pelc
• Author: Martin Greven
• Author: Rafael M. Fernandes
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

We employ the phenomenological Lawrence-Doniach model to compute the contributions of the superconducting fluctuations to the third-harmonic magnetic response, denoted here by M_3, which can be measured in a precise way using ac magnetic fields and lock-in techniques. We show that, in an intermediate temperature regime, this quantity behaves as the third-order nonlinear susceptibility, which shows a power-law dependence with the reduced temperature ε = (T−Tc)/Tc as ε^(−5/2). Very close to Tc,... More however, M_3 saturates due to the nonzero amplitude of the ac field. We compare our theoretical results with experimental data for three conventional superconductors—lead, niobium, and vanadium—and for the unconventional superconductor Sr2RuO4 (SRO). We find good agreement between theory and experiment for the elemental superconductors, although the theoretical values for the critical field systematically deviate from the experimental ones. In the case of SRO, however, the phenomenological model completely fails to describe the data, as the third-harmonic response remains sizable over a much wider reduced temperature range compared to Pb, Nb, and V. We show that an inhomogeneous distribution of Tc across the sample can partially account for this discrepancy, since regions with a locally higher Tc contribute to the fluctuation M3 significantly more than regions with the “nominal” Tc of the clean system. However, the exponential temperature dependence of M3 first reported by Pelc et al. [Nat. Commun. 10, 2729 (2019)] is not captured by the model with inhomogeneity. We conclude that, while inhomogeneity is an important ingredient to understand the superconducting fluctuations of SRO and other perovskite superconductors, additional effects may be at play, such as non-Gaussian fluctuations or rare- region effects. Less

• Keywords (english): superconductivity; fluctuations; nonlinear susceptibility
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Physical Review B
• Numbering: vol. 104, no. 6, 064502
• p-ISSN: 2469-9950
• e-ISSN: 2469-9969
• DOI: https://doi.org/10.1103/PhysRevB.104.064502
• URN:NBN: urn:nbn:hr:217:908089
• Publication: 2021
• Document URL: https://link.aps.org/doi/10.1103/PhysRevB.104.064502
• Type of resource: Text
• Access conditions: Open access
• Public note: © 2021 American Physical Society. Received 4 May 2021; Revised 20 July 2021; Accepted 21 July 2021; Published 2 August 2021.
• Created on: 2023-08-06 19:44:28